My advice would be to stay on the strip. It is much easier to walk out of your hotel and walk up and down and visit the other hotels. Each place is so big, that it is quite a lot of walking just to get through say Caesars or Venetian, they are huge.
MGM is nice but it is on one end of the strip. The walk area from MGM towards M&M world, is also getting very very crowded and a little seedy in the evening.
I personally would not recommend excalibur other than for its price. love visiting the casino itself, but it is very smoky and rowdy compared to other casino's, and appears much more crowded. We love the Palazzo if the budget allows, or Flamingo for location, great pool and ok rooms. I suppose you need to have a look at what types of rooms you are happy with, budget etc, and then look at your options on and off the strip.
Just stay away from Circus Circus! Ok to visit but not to stay there.