Let's just say the rules are very simple.
A stand-up fight/striking match for 5 minutes, just 1 round. Only strike not allowed are on pressure points/death finger and attacking vital areas such as the neck. Everything else is fair game.
I just don't think there'd be much issue with weight here. There was always an open category on martial arts competitions.
I think we are all familiar with what Buakaw can do. Unless you have banana trees as relatives, you'll surely love his ferocity and power of his kicks.
Bruce is a true martial artist however, the mystique of his prowess is also depending on your opinion affected by his movie star status. In films he looks good, perfect fighting machine actually. But is he that good in real life? Or, we have been very fortunate that a man of his talent and wisdom came along at the time that filming already existed and his brilliance was captured.
I can't give my own opinion, I'd rather get some insight from other MMA followers on ESB. But if I just have to pick, I pick Buakaw. (That's just my bias there. I fancied him after finding out the guy was born exactly 2 days after me.