I trained at TMT for around 10 months [ 2 separate trips ]. If your planning on staying over a month it's a good camp. But if you're only there short term then it's hard for the trainers to get to know you because it's such a big camp with lots of people coming and going. Also, Dragon Muay Thai is down the street from Tiger which has a more personable atmosphere.
I've never been to Horizion but I'm sure it would be a beautiful place to stay. But then again so is Phuket.