I would have to say that the larger sportsbooks cater better to horses due to the availabilty of having more TVs. I would suggest Ceasars or Bellagio. Nollan Dalla who is a big poster here at Madjacks and has a link here at the site has done reports on Sportsbooks which were very in depth and great info. You may try to email him if you can't find his great work somewhere. Good luck.
Jason