Well, from my experience, "heavily RP-enforced" usually means that you can't do much on your own, that the code simply doesn't give you much to do (maybe explore the environment and find or buy some stuff, maybe even craft something if you have the skills, but no or very few possibilities of 'interaction' with NPCs, including fights; or maybe you can fight, but won't get anything out of it because any relevant XP are awarded by GMs) I've tried three games along those lines, they all had the problem with the core members insisting on their style of play, a different approach wasn't welcome
So yeah, unless you know for certain that on an RP-enforced MUD, you can play outside the 'established style' and advance, I'm only interested in RP-allowed or -encouraged ones.
As for the relativity of a character's power, I understand the concept of wanting to be all that much "better" than a fresh char after playing for a year or more, but why does it have to be THAT big a difference? A lot of players are just used to the idea thanks to most fantasy RPGs (and of course games like WoW) and don't really know other systems. It's more a conditioning to the instant satisfaction aspect of advancing one more level and getting better at everything.
That's why I mentioned Shadowrun, it's one of the few systems I know of that has a noticeably shallower powercurve (WoD games like Vampire are other examples). Sure, after ten years of regular play (or a couple of months with the GM dishing out extremely high rewards), you'll be at a point where you can beat a fresh character in every aspect. But until then, you'll be lacking in at least one area, be it magic (defense for non-magical chars), social skills like negotiation, ranged combat, melee, stealth, ... (and, not to forget, with the exception of extremely powerful people, which any reasonable GM won't allow as player-chars, ANYONE can be killed by a suicide killer, even a 500 year-old vampire; in most cases, a lone sniper can do so)
Of course, random kills need to be discouraged in some way, be it only a small death penalty and the revenge of the victim, or preferrably something more roleplay-related (randomly kill someone and you'll be hunted down, NPCs will be hostile to you, ...; obviously, there needs to be a method to prevent a 'create char, kill, delete char, create new one' circle from griefers, but that isn't hard to do)