Okay, maybe I'm coming off as more mean/aloof than I really mean to be. Sorry about that, CadetNewb.
One thing coloring my judgment is that for the last decade, I've been involved in forum roleplays. Before SARP, I was in a future-Megaman roleplay in which I had an admin role, and tried to implement this really detailed and well-thought out system. The problem with that, though, was that we weren't playing a tabletop game where 'book-keeping' was more organic. I ended up realizing that it was too cumbersome and got in the way of the roleplay proper.
When I transitioned to SARP, I immediately felt that the freeform roleplay here was significantly superior to the method I had tried to assign to my previous roleplaying environment. There's the things you detail, and the things you
actually need... and SARP was putting the power mostly in the narrative, which was essentially what mattered in forum roleplays.
However, when I was looking into weapons, my newbie self was aving a hard time figuring out how a power armor could have a 'total annihilation' weapon in the same fashion a starship was. Seeing a plasma rifle do "heavy damage" while seeing a starship turret also do "heavy damage" was also somewhat puzzling. The [1-10] DR system first came out from my request to see this clarified.
But the [1-10] thing didn't work out all that well because it still didn't make a good distinction between the power armor and the starship in terms of damage - Mindy aether-sabers still did 10 while it was clear they couldn't one-hit kill starships.
So, we have what we have today now. I actually implemented it to make the difference there, but another thing I did try to do then was turn the ship combat narrative more like Star Trek. Which, frankly, was a mistake because SARP combat until then was generally really quick and decisive (even if I wanted more weapon exchanges). I was seeing Mindy armors get carved up bloody in moments, ships destroyed after a pivotal maneuver, and so forth.
The current DR system has you believe that having a SDR3 weapon striking a ship with 30SP diminished its health by 10%, and so you kind of expect it to be 'fairly threatening'. But in application, as a GM I found myself not really following the DR system, and going more with what seemed to make sense at the time.
This is why I champion the [1-15] DR scale I put up a lot more. It's not superfluous, gives more power to GMs to make thier own case-by-case judgment calls, sets broad perceptions more accurately and in line with the style SARP itself has, and finally gives justice to larger vehicles.
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Now that I've utterly bored you with my exposition, I'm going to answer your questions.
how do you compare one weapon or armor with another of the same class? Looking at the Mindy, Daisy (without forearm shield which you relegate to a slightly different category) and Impulse for example, how do you quantify them when comparing the three? How do you show that one armor is slightly tougher than another?
First of all, this is one notion where I feel the similarities can sort of blur together. It doesn't really affect the player that a Daisy armor could be slightly tougher than an Impulse if the Daisy is the only armor used in a plot. The Impulse is not going to matter if it never shows up. If it does, it might be close enough that the difference is actually not blatant enough to be emphasized. Sometimes, the difference is really just design and mental imagery.
I'd personally classify the lightly-armored mass-production Mindy as 'Light Armor' (4). The Daisy falls with 'medium armor' (5). I don't actually know about the Impulse and I'll be lazy and not look it up. I figure a Hostile would fall in 'Heavy' (6) - NAM power armor always struck me as being more tanky at the expense of sleek curves and a bulkier humanoid shape.
I kind of like this, because just like Ira pointed out, the terms used as self-explanatory. In two words, I manage to convey expectation in classifying the vehicle itself.
The forearm shields of the Daisy and the arm-forcefields the Mindy can generate do indeed fall in a different category which is less the 'limited risk-plotshield' barrier systems would allow and more something that rewards player action/precaution to avoid damage altogether. Both can be temporary (the Mindy forcefields is power based, the Daisy's forearm shield will eventually degrade if exposed to sufficiently powerful attacks).
If I wanted a weapon slightly inferior to the LASR in terms of killing power, but still within the same weapon class, how do I show that? But what about when comparing the HPAR and the LASR? Both are still assault rifles, but one is clearly more powerful than the other, yet without being the very most powerful weapon a Power Armor can hold; an Aether Weapon.
When I look a the LASR, I see a weapon thatès made to be good enough damage to deal with a power armor, but better suited to mow through organic targets (like the Mishhu). It seems to fit right as an Light Anti-Armor weapon (4)... which is neat because it just happens to be that.
The idea of an 'inferior' Light Anti-Armor weapon would come to me as being something with a lesser rate of fire, lesser ammo capacity, and its range, durability, ease-of-maintenance. It could be less convenient to use, but still do its job.
Sure, weapons may feel more immediately fatal (even though I think they're accurately represented) but another point to consider is how the [1-15] thing also makes weapons that are lower relevant. Take the NBAR rifle: it's fairly powerful and meant to kill Mishhuvuthyar but it's not made to kill power armor. But if we take am Heavy Anti-Personnel weapon (3) and use it on a Light Armor (4) like the Mindy - catch the Mindy off-guard and that neko is not going to like how you're digging holes in her durandium plating, to potentially dig deep enough to get at the insert and her. The NBAR might not be expected to outright penetrate it, but a couple of shots on the same spot will compromise it enough to endanger.
A Daisy's forearm guns could just be Medium Anti-Personnel weapons (2). But that will also leave a mark on a Mindy, and would be strong enough still for a Daisy not to take lightly. The Hostile, though? That Nep soldier is going to be bothered by the jostling and his paintjob being ruined, but he'll wade through the assault as if it was so much rain.
And finally, for aether: an aether saber-rifle strikes me as having a superior ability to strike through defenses. Figuring what a Mindy forearm weapon can do, I'd label it as Heavy Anti-Armor. I expect the soldier in the Hostile to see a Mindy II closing to melee and expect that forearm light-projection to kill him if it hits him. A spray of energy needles will very easily chew through his armor.
But take that against an armored tank, and the scalar radiation releasing energy might not be potent enough to chew through all the matter in the way, especially when it gets to stronger, heavier exotic material... and the bigger vehicles are also more likely to ignore an attack small enough to not cause major damage unless it's very localized.
What's more, how will it handle ships being made by less advanced civilizations?
Does it have to? From what I've seen, the less-advanced civilizations like the Lorath and Gartagens are all too keen on getting even anyhow. But, to answer your question, it's all still a matter of expectations.
I could decide to have a starship plated in stealth armor to only offer the mecha-level protection. I could vote that helicopters and fightercraft, wanting to stay light, would have 'Armor' level protections even though their size lands them in the mecha category (fighterplane fights are usually sudden-death ones).
If I use a machinegun on a Cessna plane, I expect to make holes in it that will easily render it non-flight worthy, so we could label it as personal-level protection. Sure, I don't expect the machinegun to make it explode or destroy it outright like it'd do a person, but that's where common sense and having a referee comes in.
It's the same for a guy carrying a rocket launcher. Do you expect a bazooka to punch a hole in a tank? Then it's Anti-Mecha, power armors should not take it lightly even if it's just a random Joe lugging it around. And that's fine, because it makes sense. Besides, one of the points was making non-armored infantry matter more against power armor despite the latter still retaining an advantage, right?
A big fuel tanker might be as big as your average gunship.... but it's definitely not as well protected. Odds are a starship railgun will easily punch through it and fold it in two just because it's so damn powerful.
Technology-issues might not matter as much as intent. You could say that beam weapons are more convenient to sub-luminal mass drivers, but if the end result is leveling down a city-block, does it really matter what technology it came from? Today's nuclear missiles could prove a potent threat against a starship just due to the physics behind it making it threatening. Sure, advanced tech and engineering makes the starship potentially able to survive it, but there's really not a whole lot of difference currently applied to things that can level cityblocks to weapons that are planet crackers.
Also, fluff and design still separates superior designs to crude ones. A Heavy Anti-Starship Z1 Torpedo happens to be high speed and is homing and that makes it apparently stronger than, say, a Lorath ship-mounted railgun who could fire in a linear ballistic path at a lesser speed, even though we could term it capable of about the same amount of destruction in a different delivery method.
The NSP is technologically superior to the SiZi 79... but if you shoot either at someone, they still will probably die.
A more limited race might not have capital ship armor. It might not be able to do capital ships in the first place. It could lack the ability to make armor as thin as the one you find on KFY power armor, and only see that kind of armor on thier tanks. There are a lot of ways to spin this and be flexible.
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At the end of the day, the nuances might actually not matter all that much. You mention hard numbers, but in a freeform roleplay, the only calculator you really need (and will use) is your imagination. If it's going to be this way, you might as well set expectations more simply, and give the leeway to arbitration where it will be taken anyways.
The security and assurance that seems to be signified by recording differences in hard numbers might look comforting, but in actually for GMs and players alike, it's worth
squat. Which is why I say to implement what will actually be used rather than what sounds like it would be good to use. If SARP was a tabletop game, that kind of tracking would matter, but in our present medium, it's
very redundant.
It doesn't matter that the Mindy has 6 SP, and that a tank has 20. What matters is that you don't expect the Mindy to survive a hit from the tank's main cannon. That you don't expect the Mindy to be able to outright destroy the tank since it's oh-so-much tougher than the Mindy is by the virtue of being bigger and tank-like. Odds are the Mindy-wearing neko will choose to more selectively disable the tank by focusing her attacks on its tracks, where the engine is, or somehow blasting through the hatch to get at the people driving it.
Is making a comparison between the Daisy and Impulse so important that it needs numbers to straight out express it? The description of how they work should be more than enough. Impressions will be carried out into expressions during the roleplay, and straight hard numbers will essentially be cheated. There's not much point to hard numbers if they're just going to be bypassed anyways.
