I have stayed in both places several times. I've never had an issue with the noise, but as a disclaimer, I can sleep through anything. There were times when I had a corner room at the 4Q right next to one of the stages. When I walked in the room, I thought I was going to have a problem sleeping, but in fact, I only heard them for the three or four seconds it took me to fall asleep.
MSS has a little more variety for food, since you can use players club points and often get comps at restaurants for there or the Cal. MSS has the advantage of a buffet. I used to shy away from buffets, but I had a stroke back in the fall, so the buffets allow me to fill up on fruit, salads, veggies and other healthier options and to take smaller portions of the less healthy options.
Rooms at both places are basic, but they are clean and comfortable. Neither of the hotels have much in the way of amenities (spas, fitness centers, etc.). Housekeeping is pretty prompt in both places. It's very rare than my room isn't cleaned by early in the afternoon.
Some people are a little unnerved by the walk from the FSE, since it isn't under the canopy and there aren't security guards. I have never had a problem. Sometimes I will walk through Binions and cross the street right by the Cal, but most of the time, I'll walk between Mermaids and Binions. Sometimes I'll walk right up Main Street by the Las Vegas Club. No one has ever bothered me, but then I typically mutter loundly about aliens, stock futures, or how 9/11 was nothing but a media event cooked up by the networks and their allies in the Democratic or Republican parties (take your pick) to generate ratings.
