I use the cheap Chinese 6 way switcher in my SFII cab... mostly because it's cheap. Also, since I don't switch games that often, having the unused boards off is a nice feature, so the boards aren't all soaking in the heat of all the boards running. If you switch games a lot, having them all on (like Clay's kit) would be better, so you're not constantly powering on/off boards. Clay's kit requires a beefier power supply (and/or multiple supplies) to power the boards since all boards are always on.
I've also got the cheap Chinese 2 way switcher in my Area 51 Site 4 cab. This one does power both boards, though it's only two of them, so it doesn't get too hot or draw too much power.
DogP