Fant is very versatile, and the aspect of his game that will matter the most is his blocking. Blocking will decide this position battle...McKeon is proven on the pro level, Fant looks as if his blocking will carry over to the higher level, but Louepke I haven't seen any plays with him blocking at all.
Fant: Blocking, Routes/Receiving, Running, STs?
McKeon: Blocking, Receiving, STs
Louepke: Running, Receiving, STs?
I think Fant is the most versatile of the 3, but it just depends on what McCarthy values more for the team at this H-Back position. I actually like all the players, and have no pet cats here so I can enjoy watching this battle.