My vote obviously goes to Mihawk. Yasopp is most likely a distance fighter, but Mihawk has both ranged and close attacks. Plus Mihawk could just use his giant sword as a shield from any bullets.
Mihawk is the clear favourite for this match. He takes this.
Mihawk is a close-range fighter, Yasopp is sniper. This is essentially Usopp vs Zoro - As soon as Mihawk closes the distance, he'll shred Yasopp like he did Buggy. The only chance Yasopp has is to beat Mihawk before he has a chance to get close, but given Mihawk's reaction speed (such as slicing off Luffy's arm when Luffy uses a gear 2 Jet Pistol) he won't even get close to getting a good hit in.
Josef, it appears you forgot to put the poll. In anycase, Mihawk got my vote if you count posts only.
Why? Mihawk deflects bullets with his sword
Wow! The best swordsman vs. the best sniper!
But since Mihawk and Shanks always fought to a draw, and Shanks is Yasopp's captain... I have to go with Mihawk to win this one.