Speaking of the devil,
I had the same dilemma as you. I started out trying to use WiiFlow for GC/Wii loading. The issue I ran into was that Dios Mios/Devoloution/Nintendon't route is just not compatible enough, requires updates and lots of troubleshooting. For whatever reason, I couldn't even get DM to work at all. Devolution would be nice, but the anti-piracy protection limits you severely and you need a DD to scan in games. Nintendon't is just too young for good compatibility.
While WiiFlow can run Wii games fine, it does misbehave from time to time. Crashes and DREs were very common for me. I ended up just using it as the front end for the Wii, since you can operate it with any controller and access HBC software, emus, etc.
A WASP with Swiss flashed was the solution for me. Boot to disc from WiiFlow into swiss and there's your GC titles, or load a WKFdol to boot into stock firmware and there's your Wii games. You have to swap SDs but for the sake of simplicity and reliability I think it's worth it. By all means give Wii loading and DML a shot, but if you run into issues I'd cut your losses and buy a WASP.
I also tried a hybrid approach, where I used the WKF for GC titles and Wiiflow for Wii games by connecting the DVD drive PCB to the WKF passthrough port. Unfortunately, this method only resulted in DREs. I changed PCBs, drive power and FFC cables to no avail. It seems that WiiFlow doesn't like flatmode.
If you can somehow get decent GC emulation working, go for it. Personally though, it isn't worth the trouble. I had 2 boards brick because of Priiloader and CIOS issues related to WiiFlow loading, so be careful. If you end up using a WASP and need the DOL files for booting into the stock WKF firmware (for Wii loading), Mega probably still has them; if not I have copies and if all else fails they are buried under pages and pages of threads on GC Forever.
Good luck!
