For past SEMA events, I've stayed at:
Paris
NY NY
MGM
Encore (Wynn)
Palazzo (Venetian)
Nicest rooms have been at the Encore, by far. We did a suite this last time at the Palazzo, it was also very nice.
Convenience-wise, I prefer MGM the most. Why? It is the first stop for the monorail, so you get onto it first in the morning. Hotels down the route get greeted by a full monorail that sometimes can't hold any more people.
I'm going to focus on just having quick access to the monorail from now on. Sucks walking between hotels each morning, and through various casinos full of cigarette smoke just to get to the monorail. Especially with a hangover