As a gambler I have been comped to high-end rooms at both Wynn and Skylofts. They are both excellent in very different ways.
It depends on your personal taste. For me, the Skyloft is the modern apartment I never had. So they are my favorite rooms in Vegas right now.
At the high-end they are both great. But a low-end room at Wynn easily beats its counterpart at MGM just by being newer. They are renovating everything at MGM, but from the top down.
Traveler