On shmups forum someone did a comparison with Wii vs Gamecube and Gamecube ended up having a clearer/sharper image, but later on in that thread there were rumors that the newer Wii has higher video quality so I decided to test all the consoles using 240p test suite to 480p and have all the systems run in 4:3 480p. My capture card unfortunately only runs in 720x480, although it doesn't seem to stretch any of the images (from what I can tell). I used this capture card and the same Rocket Fish Component Cable for each system except the Gamecube in which I used the official Gamecube Component Cable. The tests are done via 240p test suite being scaled to 480p done in the same fashion as the thread on shmups by Sixfortyfive. RVL-001 / RVL-101 Gamecube / Wii U You can see the full album for more comparisons here, the pics shown in this thread are a demonstration so I don't fill up the thread with a ton of images. RVL-001 Wii (First Wii) RVL-101 Wii (Second Wii) Gamecube Wii U I have a feeling the Wii U tests are inaccurate as I notice the quality is considerably lower, I assume since the Wii U is incapable of 240p that might be it, but I honestly do not know. From what I can see, the Gamecube has the highest quality image and sharpest image, where was the RVL 101 Wii comes in second with better image quality than the first generation Wii.
It's actually a considerable difference, but if you can get by with Wii you'll save your wallet a lot of money. Look closely at the lines. Old Wii / Gamecube Old Wii / Gamecube New Wii / Gamecube New Wii / Gamecube Versus the old Wii it's a lot clearer and better with colors, you can tell by the first image when you compare the lines. Versus the new Wii, the newer Wii is much sharper than the Old Wii, but when you pay attention to the second image, the Gamecube is a lot sharper still. Although, the New Wii doesn't have the issues the Old Wii does with the lines in the first pic. New Wii is actually a considerable improvement over Old Wii. I created this thread to actually confirm that question. So, yeah. If you have money to burn get a Gamecube controller as it is a considerable improvement, but if not, stick with Wii cables you'll save yourself a lot of money.
You're welcome! Unfortunately I don't have a Wii Mini, but since the Wii Mini only supports Composite (I don't think it supports S-Video either from googling), so there wouldn't be a test I could do unless someone some how modded Component onto it. Wii Mini lacks online features such as the Wii Shop, SD cards, Soft-Modding, Gamecube Controllers and is stuck to Composite Video. I guess a Composite video test could work but I don't think that's really necessary.
The Wii U also has HDMI output, right? That's probably the best option for that system, though it depends on what type of display you're using.
You can't play GC games on stock WiiU, but if you softmod vWii mode, you can run this to play GC games.