ProtPaladin uses ProtWarr's basic framework instead of something unique.
Tankadin is currently more "accurate" when it comes to displayed stats and support for Librams, but that's the extent of it.
ProtPaladin is a lot smarter in the way it does Threat Rotations (and is incredibly easy to modify), complies with the Survival and Mitigation ratings used by the other models, and has all the pretty features that ProtWarr has that I wish that Tankadin
Tankadin was rather convoluted in the way it does some of its calculations, and it was much much easier to use universal calculations that are almost exactly the same as what ProtWarr would use.
Any changes to ProtWarr or ProtPaladin's shared components now translates easily to the other.
The only reason there are *two* Protection Paladin models at the moment is to ease the transition and testing process on me and my collaborators. That's all.