Well considering the amount of emu's x-port has "ported" over to the xbox. I would say that he has the most experience.
Although he is nowhere near as active on the xbox as he used to be..
As for me... outside of updating cores and importing specific sections of emu code on x-port's emu's. I have not really done any direct "ports".
Nes6502 has ported "snes9xbox" and some other stuff? Did he do all the Doom, Heretic, Hexen, Descent, Quake 3, and stuff? I honestly don't remember who did those.
There may be a couple more oddball emu's out there but I don't remember off the top of my head.