PS4.
As Tom said, controller tech isn't there yet for next-gen, so more people are playing on the console with a stronger pad for FGs. Neither pad is great, honestly lol, but PS4 is better for FGs as a whole. Also, a number of FGs, most notably Street Fighter V, are being released exclusively on Sony consoles. Unless that changes, the only reason to own XB1 for FGs is for KI in that sense, unless the multiplatform games run better on XB1.
In all honesty, the performance concern shouldn't be one, given that PS4 and XB1 run on similar enough hardware, though it should be noted that PS4 is capable of playing games at 1080p at 60fps, something XB1 doesn't do. Some XB1 versions of games actually don't even run at 60fps, while the PS4 versions do, so that brings into question exactly how stable of a performance XB1 actually provides in comparison. DirectX12 should help the XB1 here, but for now, the PS4 (so far) seems to actually run better.