Have you seen the Protector? He did one continuous shot of him fighting up stairs for something like 4 minutes and it only had to stop because the cameraman was tired from walking up the stairs (i think it was 4 stories?).
Muscle and size doesn't mean anything in a fight, Crocop vs Sapp proved that. Michael Jai White probably isn't that great of a fighter either, but we don't know since we've never seen him fight. Bruce Lee never fought anyone on camera or in front of a crowd, but have you seen his sparring video? The dude is lightning fast
Size does matter. If both fighters are equally skilled then the bigger one will win, its simple logic. Smaller fighters only win if they are more skilled and even then the size has to be somewhat comparable.
Have you seen Hero with Jet Li? You know when he fights that big ass dude in the ring? Even Li himself said that in a real world situation he would have had his ass handed to him because that guy is a fucking tower.
Im pretty confident that I am stronger than Jaa, and my reach is longer. So if it came down to it, my elbow to his head will impact with a greater force than his would. He doesnt have enough skills to win a real fight based on that alone in my opinion. Wow, he would do a flip. Woopy.
For the record, Ive studied Muay Thai for a number of years and now train Krav Maga and BJJ.
I know plenty of Muay Thai fighters that would absolutely murder Tony Jaa. Other than his stunts, he doesnt impress me at all.
Where as Michael Jai White, I wouldnt want to fight him, he has some amazing power while at the same time being so quick and agile. Same with the likes of Scott Adkins who is just a freak too.