knowing more how you want to play would help, whether you like pressure or want to be the guy doing work behind the scenes, whether you want to dictate the team's play or not, or if you like to be creative or prefer brute force.
my opinion is if you want the team to hinge on you and enjoy the challenge of succeeding under constant pressure, then med's the way to go. you can also dictate play, but the pressure on you is immense to keep heals up and stay alive.
pockets tend to be forceful and can dictate the play a lot and often get a lot of the praise for their team's success (aka you can be the hero you always wanted to be), whereas a roamer has some more freedom and can be more creative (let out the artist in you?)
scouts can do crazy work, especially if your dm is top class. you can be a killing machine if you're a good scout, and being a light class there isn't too much pressure on you as you are not typically leading the push.
these are all just generalizations, there are always exceptions of course.