My favorite is "Lose It!", for it's interface and how easy it is to use. MFP is what I use now just because it's what all my SG forum ladies use If my SG friends didn't use it, I would use Lose It! instead.
I still love bodyfitness mostly as it not only shows how much kcal are there for you to use for that day, how many are left (counted accordingly to your preferred weight lose of the week to reach your goal) but also amount of protein, carbs, fat for u to use, how much have u used and how much is left... Oh its great