I call it "rules medium" because it's crunchy, but not finicky or memorization-heavy in the same way that, say, 3.5 D&D is. You can build straightforward characters quite easily, as the rules for each effect (and there aren't that many, and a good portion of them are situational) include all the modifiers you'd expect to need. Besides, it sounds like whisperwind1's complaint is about rigidity, rather than complexity-- they mentioned disliking how vague FAE characters are, for instance-- and M&M is all about flexibility-without-being-vague.
As for Dungeon World, unless it's been significantly tweaked from the version of Apocalypse World I played (which doesn't seem likely, based on Friv's summary), it has a major tone difference from traditional RPGs: the expectation is failure, and plot progression by "failing forward." You will screw up fairly consistently, with nasty, nasty consequences throughout. Which can be fun, but it's a drastic departure from many other games.