Muai thai hands down. Its kickboxing on steriods
Muay Thai isn't the best. It's way too legs-orientated. It's because Muay Thai matches are judged much heavier on kicks, they don't spent enough time boxing to be able to defend against boxing.
I came to this realization just under a year ago, after studying and practicing muay thai like a religion for 3+ years. It was sort of a hard pill to swallow but dutch/holland style kickboxing is simply the more effective style in a limited rules environment.