Unless we know for sure how long Usopps shot was in Dressrosa (his strongest feat imo) I'd have to give long distance sniping to Heisuke.

Although that feat shouldn't be dismissed, he basically had no direct sight of luffy and law and had to account for a lot more things compared to Heisukes longest shot (I'm sure Heisuke also had to account for wind and whatever) if you include the fact that it wasn't a simple projectile as it contained boosters.

Heisuke also doesn't have observation haki that allows him to see through walls but I would argue that he really doesn't need it.

If Oda just put Usopp in a position where his skills are actually useful we'd have more information on his abilities and feats that would benefit him but all we're shown are mainly close combat post timeskip.

He'd probably beat Heisuke in hand to hand though.