They are both nice areas....
Helena is an old town and still maintains a genuine little downtown area that has been praised in the national press.
City of Helena, Alabama: Living in Helena
Pelham is a very rapidly growing area...it has an interesting angle to it that the others don't. If you like to play either golf or tennis, the City of Pelham has superb municipally-owned golf and tennis facilities.
Pelham, Alabama: Racquet-Racquet Club
Ballantrae Golf Club
The mayor had a goal to make their golf and tennis facilities so good, that you wouldn't need a country club and he succeeded in a big way. Pelham also has a very nice civic center which includes
two large ice skating rinks.
Trussville is also nice and has good schools and is growing its retail in a big way. The advantage you would have living in Trusville vs. Pelham would be your drive to work would be a bit easier as I-65 North is pretty clogged in the mornings vs. I-459 which can carry heavy traffic better.
I think all three are good choices frankly....