A couple things to comment upon:
1. As far as the linear d20 vs bell 3d6, I find that at extremes both systems tend to break down. I suppose each can have a preference, but at least a d20 is more predictable than 3d6. What I mean is that a +1 is the same no matter where on the d20 you are, but a +1 can mean different things in the 3d6 roll. Far too many gamers and game designers really don’t have a good feel for numbers and haven’t a clue what this means as far as play or game balance goes.
2. In a level-based game, a higher level character is better than a lower level character. In a skill-based game, a more skilled character is better than a less skilled character. If a character has more luck, karma, fate points, fate dice, or whatever, that character will be better than another who is lacking those things. Any imbalance in the game is a function of the GM running the campaign, not a fault of the rules.
3. While not a fan of the d20 system, I am a fan of the original rules on which they are based. Original D&D was built on a level system and allows for progression at a slow or fast rate, depending upon how the GM wants to make it happen. In my campaign, I don’t bother to count experience points but instead award levels as they are deserved. I often start characters out at third level and we slowly advance until eighth or so, then generate new characters and start over. Do characters get better in jumps? Sure, but it’s really more gradual than it sounds because not all characters gain a +1 for everything each time they advance. A skill system does a similar thing, only the players have a bit more control over where their advancement goes. I prefer a class system because it has a nice template and makes it easier to generate NPCs and easier to advance characters.
All of this is academic. Dresden Files will be based on Fate3. Track down a copy of Fate and look at it rather than debating the merits of other game systems which are not really part of these boards anyway.
Just my two cents.