my 2 cents on D&D/pathfinder
when you look at armor values defenses tend to be HIGHLY stagnant and most armor is effectively hardcapped at ~9-10 not counting magic bonuses.
example I dig out the PHB armor table version 3.5
http://www.dandwiki.com/wiki/SRD:Armorwe look at the light armor and it all caps (except padded) at +8 total bonus, padded is capped @ 9
medium armor (except breast plate is effectively capped @ +7 bp is capped at 8
etc. once you get your armor vs dex maxed out, other than adding things like shields, magical bonus's natural armor etc you are pretty much done. the only place you can really go is exotic material which tends to more or less modify/break the standard armor limit rules.
example mithril (sometimes nicknamed elven silver or elven steel) is twice as strong as regular steel for the same weight, (or a bit more, honestly but for all practical purposes) so if I get a suit of elven chain vs std chain the std chain is going to weight 40 lbs, the mithril equivalant will weigh closer to 20 lbs but it provides the same protection unless enchanted (magic) which it usually is.
so back to theory craftinga moment... you make a human fighter with 12 dex (dex being the defense stat) you manage to get the gm to let you get banded mail armor at 1st level or so yay 250g worth of armor, and your defense is effectively a 17 (armor and dex bonus)
I make a elven fighter and manage to max out my starting dex for a whole whopping 20 giving me a +5 active defense I can't afford elven chain plus 5 armor bonus max dex of +4 nonmagical the stuff costs 4,150 gold pg 220 3.5 DMG
so I am stuck with chainmail with its max dex of +2 meaning that even though I could get a bonus of +5 in regular clothing or studded leather I am capped at +2 if I go with actual chain which then has an armor bonus of +5 from an economic stand point I would get MORE protection from studded leather (at 25gp) +3 armor +5 max dex, than I would with a full suit of chain mail +5 armor, +2 dex max which costs 150 gp
note this doesn't take into account issues like differeing protection based on attack type blunt vs slashing vs piercing but you get the idea
additionally a lvl 20 warrior can get the same protection out of a given set of armor as a lvl 1 char can.
its an issue I have seen for a while but I am not sure how to resolve it.
when you go with the D20 star wars they went the other way, giving all chars a defense adjustment that increases with level, but is reduced/nulified if you wear armor so congradulations there is now basically NO reason to use armor...
the only thing I can really think of is to sort of combine the options but then you get situations where a high level fighter could walk through an army of low level shlubs (mobs) and they could NEVER touch him