Compared to that other Super Hero MMO I used to play, CO is better in my opinion. That " other " Super Hero MMO kinda falls flat after their level cap. They have a lack of missions so you pretty much repeat the same content over and over again which you have to pay for. CO seems to have quite a bit of missions from what I've seen so far.
That " other " Super Hero MMO isn't solo friendly like CO. I like an MMO that allows you to group up or solo instead of only being able to progress in a group.
The character customization is far superior and unmatched compared to that " other " Super Hero MMO. Not only can you customize your appearance in detail but you can customize your combat and powers. That's something I haven't experienced in any MMO other than CO at the moment.