Wow, the thread was so interesting and on topic yesterday... before the those with post- traumatic road rage jacked in to knock the things they no longer enjoy.
Hero and M&M can both add insane dimensions to your game. Some fans of either system seem to find that the best way to promote their "fave" is to knock the competing systems. Heee yaaah. Have at it.
If the OP is looking to seriously buy into a superheroes game, the best bet would be to drop the dime on supplements for both systems (and a few point books to boot). M&M and Hero both offer specific perks and liabilities which is best for the OP depends on what he/she wants in a support material.