I'm not the guy you were talking to, but in a game without level scaling, a wide power range effectively means less choice for the player. Because more things will either be too challenging to deal with, or too weak to provide a worthy challenge.
You seem to be using a different definition for "power creep" than he. He seemed to be using it to mean the character is OVERpowered (remember, we're talking about level caps, which he supports and I definitely do not). Which creates the exact opposite situation--the absolute most amount of choice for the player. You can throw your party full of tanks at an enemy and succeed. You can throw your party full of mages at the enemy and succeed. You can use a conventional party of a tank, damage-dealer, healing mage, and damage-dealing/AoE mage. Or you can go it alone and survive.
Remember, this is a video game, where the only real option in a combat situation is to succeed. Things that prevent you from playing the party you want to play [because a level 30 mage can ONLY be a damage dealer or a healer, or have a modest amount of constitution, that they're mutually exclusive (this is hypothetical, we do not know if this will be the case)] can ONLY, ONLY, limit your combat options. Not that limits are a bad thing always (any artist knows that limitations are where skill shines through), but when it comes to roleplaying they are.
The only "problem" that having an overpowered character brings could be that the combat is not a challenge anymore. Which is exactly how I want it. I don't care about playing on Nightmare. I don't care about games that are all about how hard they are *COUGHDarkSoulsCOUGH*. I don't play games for that stuff. I acknowledge its value, but I don't acknowledge any need to keep me dependent on the system.
Comparatively, I play Need For Speed games and the worst thing, the worst thing in the world that drives me crazy, is rubber-banding. level-scaling feels like rubber-banding. Level caps, low ones anyway, can easily feel like rubber-banding.
This is out of place, but it's following my second paragraph. I want to be able to play a dual-wielding rogue (with a longsword preferably, but Bioware isn't supporting that anymore), one who is admittedly very weak and inaccurate initially, but as levels go by, gets much much more accurate and stronger, and who by the end-game deals more damage than anyone else, and takes less damage than anyone else. Will only 30 levels allow me to do that? Not a large concern, but definitely a concern.