Sean: None of the casino race books set their own odds or set up separate pools anymore. All of the money bet goes directly into the pools at the individual race tracks. So from an odds or cost standpoint it doesn't matter which casino you choose.
So it would come down to comfort or preference. Simply put, the nicer hotels have nicer race-books. My wife's personal favorite is Wynn. She prefers the setting, and the desks there. But most important to her is that she can plug a headset into her TV (not possible at most places) and shut out the rest of the world and watch her race.
I've never been to where you are staying, but I believe it is south of the Strip hotels, so the nearest nice hotel to you would be Mandalay Bay, which does have a comfortable race-book.
South Point is also close by. Not fancy, but the race-book is a favorite of locals.