With bmac's suggestion, I decided to do some testing on the load time differences between the GCN and the Wii. I ran a test with a total of 8 runs of Ison Corridor Ambush, 4 runs on the Wii, 4 runs on GCN by Ninjafalcon_2. I chose this level because it contains the most common amount of cutscenes and level changes (4 cutscenes, and a change level half-way through), plus it's fairly short. We both mashed through the cutscenes as fast as possible, so there should be at least a few frames of variance between them because of this.
This game runs (I'm pretty sure) at 60fps, but I could be wrong. Regardless that is what the fps was set to both of the recordings I have. I counted the amount of frames between all the possible loading variances between all of the runs, and averaged them out. you can see the data in the spreadsheet here:
My results are suggesting that it might actually be slower to run on the Wii by on average about 1/2 a second per level if they have the same amount of cutscenes and loads as Ison Corridor Ambush. Not an significant amount of time for ILs (might be worth playing GC for WRs though), but possibly 3-5 seconds on an any% run.
BIG HOWEVER though, with such limited testing, the results are inconclusive. The runs are not the same, and performed by 2 separate runners, so button mashing speed could be causing this too. But we do know that load times are inconsistent, aside from button mashing.
More testing is obviously needed, but it's pretty time consuming, and I'm not sure where my GCN composite cables are... so as of right now I don't have a way to capture and record runs on there.
If anyone is interested in helping me gather more information, please let me know. Please also feel free to suggest any other ways we could time this consistently.