If we are considering that both are in their prime, we can take a look at JCVD's kickboxing record, and Michael Jai Whites experience, in that area JCVD would have an advantage due to having experience in the ring, but at the same time MJW did have some street fighting experience if I remember correctly.

As for who knows more, JCVD knows Shotokan, Muay Thai, and TaeKwondo.

MJW is a black belt in seven different martial arts, so he wins that portion.

With size and reach, well MJW is at least 6'0'' tall, while JCVD is at...5'10'' maybe 5'11', so a bit of a height advantage. And I'm unsure of what the reach is.

I mean, I'm a fan of both of them...but I think I have to give this one to Michael Jai White.

Van Damme is old now... chance are for Michael Jai White

No one.

I know that sometimes these "who would win" questions get dull. But I think this would make for a fun exciting fight had it happened in their primes in a real martial arts tournament.