Favorite: I've stayed at many of them and I have to say that I like a lot of things about The Venetian. Now you have the Palazzo beside it as well. Just good restaurants and shopping around there. Plus, I usually do well in their casino!
Least Favorite: The Tropicana. Years ago, we had a water problem in our standard room, and they upgraded us to a full 1 bedroom suite which was just as bad. Noise, broken equipment, etc.. Nasty stuff.