When I was first working on my Nexus D20 system I was thinking in terms of Classes such as in T20 Traveller and Spycraft 2.0. I was mixing it with my idea of having Feats under Skills. I had more and more Classes and they were less and less different from each other. After a while I realized that I could make Classes all day long but there wasn't much point to it because it was just proving that the game system didn't need them in the first place.
Basically I think that level based games are starting to shed their need for classes. They have been together for so long that most people don't see how that could be but we have Mutants and Masterminds and D20 Call of Cthulhu already that don't have classes and they work fine without them.
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My limited experience with GURPS indicates that it's a lot more predictable with lower point (gritty) settings, where the variance of abilities isn't so high. Once you get to higher point (super) settings, making such assumptions about PC abilities is very much more difficult: there's not really much of a baseline.
Considering that M&M virtually gives up on balancing such characters, GURPS is definitely in the top tier of such games.
Unclassed systems are harder to design and harder to learn.
GURPS remains the only game where I saw system mastery really being abused - a few players who were very familiar with the system produced some horribly unbalanced characters that were well within the rules, and this was without using Supers.Hr. I find GURPS Supers to be among the worst of such games, rather than the top tier. I find more balance inherent in M&M than in GURPS. Heck, I find more balance inherent in FASERIP, and that's saying a lot.
Different strokes for different folks, though. Perhaps we just interact with the balancing issues differently, and so find more strength in different places.
Hr. I find GURPS Supers to be among the worst of such games, rather than the top tier.
How recent if your experience with GURPS Supers? GURPS 4e substantially changed GURPS Supers. Older versions were kind of a mess, although I would still say Supers second edition is at least on par with FASERIP, rather than worse.![]()

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.