What exactly do you want to know?
The Wii's softmod is a lot easier to do but the only emu's I've ever used on it were NES, Genesis and SNES. The controller options for the Wii turned me off from using it for anything besides wii/gc games.
The Xbox softmod can be a huge pain. There's a couple different ways to do it so it'll come down to personal preference and whichever you feel more comfortable with. Coinops is what I have on my Xbox and I couldn't have asked for anything better. Although, upgrading the hdd is another huge pain, and transfering the coinops files over is a lengthy process...It was well worth it to me in the end.