I'm betting on Hisoka because this is one fight he's been looking forward to but also because he's one of my favorite characters, I'm stuck between him and Ging.
However, Chrollo is not to be taken lightly, especially since he felt the need to get new abilities which aside from showing Hisoka's level of power also implies that he believes he can beat Hisoka now. We know Chrollo is a smart guy so there is definitely something behind his confidence. What's backing his confidence is a certainty of the outcome of this fight. Remember, Chrollo challenged Hisoka when he felt ready, in other words, he chose the time and place. He even mentions how winning in style is more important than just winning which supports that. Anyway, I believe Chrollo used Neon Nostrade's powers to predict the future and found the right time to challenge Hisoka. The predictions are a 100% accurate but once you know you can avoid it. This is why he was on the run from Hisoka, he was waiting for the prediction to result in his favor before facing Hisoka. This must be what Togashi have done unless he made Chrollo dumb for the sake of plot like he did the Phantom Troupe members when Hisoka changed his prediction by not seeing his Bungee Gum.