I'm new to Pokertracker and pokersoftware tools in general - whats the difference between Playerview, Gametime+ and PokerAce HUD ?

I know Playerview charges $50, GT+ is free (but requires PT) and PokerAce HUD is also free, but I dont understand really whats the difference between these 3 applications?

And what would you personally recommend me to use, now that I'm starting using PokerTracker