All of them
Depends upon the manga at times but the general reasons are:
Better story
Better art
Better character dev.
Better fanservice
and many great stories that have not yet been made into anime.
Anime generally you should watch for the few that are not manga(Light novels) or the action scenes.
i also read naruto and fairy tail and thats about it.
I think fairy tail does a good job on intro work for new powers, but atm(outside of the dragon-fest) everyone seems to have these ridiculous powers, then another person comes along with an even more ridiculous power. Its like "hey i can control gravity" "YEAH WELL I CAN CONTROL LIFE OR DEATH"