Hardwaymoney,
I guess the topic of your thread got reduced which book is the largest. All of those mentioned above are big and good books to watch games in. If you are interested in watching "COCK"tail waitresses, the Palms always has nice looking women walking around, but the book itself is pretty small. The Rio used to be good, but the quality of the women has seriously diminished. Mandalay Bay and Ceasars are also solid. All the big casinos are packed with people.
I work out in Vegas and used to haunt the sportsbooks, but now I usually just stick to the hotel I'm staying at, because I got tired chasing lines. Every casino is going to have line movements, and you might find a favorable line for a specific game at one hotel, but the same hotel has inferior lines on another game you want to bet. You used to be able to find better lines at the smaller and older casinos (try the Orleans or Harrahs), but I don't find that to be true any more...in fact, just the opposite. Since I have a laptop with me I get to check a hotel's lines versus my offshore accounts (which almost always have better odds).
The best advice I can give someone is to go to the casino you like to hang out at, enjoy the games and the atmosphere, walk around alot, and have lots of drinks.