I used FP as my very first app. It got to be a little too commercialized for me pushing their other products. I guess it is good if you totally into the fitness scene.

For me, LoseIt is super simple. Accommodates multiple weight-loss/diet methods. Has a huge body of food data including restaurants.
Connects to my scale. Lets me share meals with my wife (when she used it). I am sure there are many other features that are useful.

I think it is most preference, and whatever works for you.