^It totally depends on your play style. I went with a Titan because I like standing my ground, laying down a lot of punishment, and having the capability to absorb a lot of damage in the process. I like the heavy weapons, armor and strong support abilities that come with this class. if you prefer a more subtle approach, like stealth and long range sniping, then the Hunter is probably more your cup of tea. The hunter is a fast mover and can really get around quickly, but they are pretty weak in terms of ability to withstand damage. Finally, if you like a middle of the road, jack-of-all-trades, but master of none, then you may wish to consider the Warlock.
I also like the Titan because I play a lot of solo play and the Titan is a good class to manage without a party supporting you.