On those mentions above about possible damage then i couldnt say that it woudl really be just similar to boxing.When it comes to impact then bare hand or no foam type of hits could even give more
possible damage.
It looks like it's more aggressive than boxing, so are the long term injuries, because boxing athletes dodge many punches, while in slapping all the hits literally fully hit the adversary's face without any chance of minimizing the damage received. Slapping is mostly about resistance and strength. Boxing involves some other skills like dodge that are always useful when facing a big challenge.
Due to this fact a weaker boxing player can overcome a most powerful one if he uses a good strategy. The same doesn't apply to slapping, so it's also a more obvious game, easier to predict the results.
Yes, it is very easy to predict in a slap tournament, just look at the large body size and strong hands will definitely win it.
because a big body and strong hands will produce a scary slap and will cause damage to the face, slap tournaments don't require a strong physique and as far as I know only doing fitness or lifting weights to produce a strong slap, and also strengthen the face so it's not too painful to receive the opponent's slap.
when compared to boxing I don't have much to comment because of the many differences especially timing.