Hi!
I'd also add that the Xii-Boy Ultra is smaller than the Gboy, meaning it's trickier to fit things inside. You also need to sand the Wii motherboard more. But overall, I consider it as simpler considering there are no wires at all. The wirefree system is great, but also risky, since you can't test things by things, you need to connect everything together and see if it works. It's harder to test, but way faster to assemble or disassemble, and once you get a working unit it's just extremely reliable and easy to take apart.
It's also pretty tricky to assemble the Xii-Boy Ultra boards, since they use really small connectors, but can be a good experience if you have the knowledge
Otherwise, I'm working on kits that will come somehow soon, to make yours the easiest way possible. No need to assemble complicated boards, they would be sold assembled! I'll make a post in my worklog soon to talk about it
Feel free to contact me over the server or on Discord, I'd be happy to help if you have questions