Jarvan is a dunkmaster.
That should answer your question.
both of them have the ability to do "more with less", but they are situationally dependant on both your own and the enemy team comp.
obviously jarvan is better with more ranged champs against melee, and xin is the opposite due to their kits
Xin now, but I expect him to get nerfed because of how well he's doing at LCS, so gonna go with J4.
Well Jarvan ganks require you to land skill shots, so if you suck at them, you should take Xin. Jarvan is more fun though.
J4 has more tank/utility.
Xin has more damage/duel potential.
Pick J4 if top is a damage based top and you need someone to start the fights.
Pick Xin if you have a tanky top who can follow right after they initiate.
J4 is better in team fights and his more tanky than Xin
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