While at first glance that adapter appears to be superior as it does more for around the same price, the biggest difference is that's really a Gamecube adapter, not a Wii Adapter. This adapter is fantastic if you've got the itch to play digital controller driven Gamecube games and of course the almighty Gameboy Player, but fewer and fewer Wii games are still supporting Gamecube support and some are only going Classic Controller now, such as Megaman 9 and 10.
Since the Mayflash adapter plugs directly into the Wiimote, the NES and SNES controllers are reconzied as Classic Controllers, not Gamecube controllers. Not only can you now use those controllers to play Megaman 9 and 10 and other VC and Wii games, you can also do so semi-wirelessly. My tut shows how to modify the Mayflash adapter with a real NES port. A bit of work but well worth it if you want to play Megaman 9 and 10 with a real NES controller to compete the experience.
shenske no offense intended, but I find it puzzling you would use MMAC as an example for why the adapter you linked to is so good. With any of the other four adapters, wouldn't the control still be reversed on every controller? I love Megaman more than most people would find healthy and I own MMAC for all three consoles, but man the backwards controls make the GC version nearly unplayable. I was able to do so only because it was the first version I bought and I wanted to see the G4 interview so badly I was willing to put up with the shotty controls.
That being said, I've seen that adapter and I've thought of picking it up. That adapter converts NES/SNES/Genesis/N64 to act as Gamecube controllers. Can you please list the button mappings for each? NES should be easy to assume. Use this formula.
NES GC
A A
B B
Start Start
Select Z
Does it support The Six button Genesis controller? What about N64 accessories like the Rumble Pak?