M&M 2e is, essentially, a level-based system, in my eyes, in that attack, damage, defense, skill ranks, and the like are capped by your level. Yes, there are many more things that aren't, but at each PL increase you get more points to spend, and your cap goes up by 1. That's just about the definition of level-based to me, even though it's so freeform in so many other ways.
Regardless, it's a really fun system, and I routinely run the bad guys / good guys on the fly, with no prep, because I know that if I took the time, the system would let me build it. Why write it all up when I know it's there, somewhere, deep down in the system, and that'd just waste my time? It's a very freeing experience, and it's a very nice system. As always, play what you like