Never been to either MB or Luxor, but in terms of perusing other Vegas sites have never seen either listed among the "top" buffets. I will say of ones I've been to that I quite enjoy Paris, Aladdin, and Bellagio. Paris' setting is unique--Parisian "street scene", and less hectic and sterile than other buffet rooms. Aladdin is cheaper than Paris and Bellagio and tries to incorporate many different ethnic cuisines--their Middle Eastern station especially is unique. Bellagio, while in a boring room, offers some excellent choices. Last time I was there I had lots of crab legs and even some Kobe beef. I haven't been to Wynn or the newish Mirage buffet yet, but would be interested in trying both. Don't think you can go too wrong with any of these. Sadly, while lunch is a better option pricewise than dinner (and if you eat A LOT you could even skip dinner ), some of the more enticing options (crab legs, for example, at least at Aladdin and Paris) aren't available at lunch.

If you are there on a Sunday, you should try a champagne brunch. I keep wanting to try Bally's champagne brunch. I agree with the previous poster that in general Bally's food offerings aren't top notch but supposedly the Sunday brunch is absolutely impeccable.