Well, the Aro'Kai model is more professional-looking, since that is what they were basically aiming for - A realistic style. As Feareh mentioned, their models are more professional since they are taking their time with the game. Feral-Heart's models give more of a cartoon-ish sort of look to it. Both are nice, but if I did have to pick which looked more detailed, or slightly better, I would choose the Aro'Kai model, since I prefer this one a tad bit more.~
(Then again, both can be professional-looking, but it all depends on how the maker wants their creation to look (or what somebody else prefers) - realistic or not.)