It depends how serious you are with your wagering. If you are just starting and doing it for fun, excitement, and trying to earn a little cash.....I'd go with 5Dimes..........no question about it!!!!!
If you been at this awhile and won't hurt to have a few outlets.....I prefer.....
5Dimes
TheGreek
BookMaker
Matchbook
Legends
and it doesn't hurt to have a local (just because)
Good luck and have fun......don't let sports wagering/handicapping wear you down......