I will say this about M&M/DCA, my party has never laughed so much during a single gaming session and I think that says something about the game itself. From my first attempt at running this kind of game it is clear that it is not as rules heavy as Dungeons & Dragons 4th Edition is. My players where able to focus more on the story and worry far less about dice rolls. They all loved it.
As my gaming party showed up for our weekly game night know one knew which RPG we would be playing. No one had any prep and no one had any character sheets. I thought it might make for a better surprise if we just jumped in and I think that worked.