Before Parker and Wiggins faced off in the all-star games, I was squarely on the side of Wiggins because of his greater athleticism but after seeing them face off, I think it might be a wash. For one, I definitely underestimated Parker's athleticism. A good indicator of his athleticism is that he has very good build up speed and his excellent handle lets him maximize it. When he gets a rebound and brings the ball up the court, he is far more dangerous than I thought. He has that freight train capacity.
Another thing, Parker is just so skilled. For him, it's all about becoming a more accurate shooter and toning up his body but everything is already there. The footwork, the shooting mechanics, the post game, the in-between shots, the three-point range, the court vision. He has a Carmelo like body and skill set with what looks to be a better team mindset.
Wiggins has much further to go. He looked like a twig up against Parker but that's fine for his age. I'd guess his frame might like Paul George's eventually. He gets harried after five or more dribbles; he's going to have to work on that to become more of a featured player. His shooting mechanics aren't odd like Marion's or Martin's but it's abbreviated and hoppy. He can get his shot off in a half-sized phone booth but I don't know if that's optimal.