I went through and timed all of the load times of three different runs by the frame. One for Gamecube, Wii, and Nintendont on a Wii with USB loading.

These were the results Wii is faster than Gamecube by: 00:02.85

Nintendont is faster than Gamecube by: 00:23.65

Nintendont is faster than Wii by: 00:20.80

You can view the spreadsheet with time calculations here. https://drive.google.com/file/d/1nw5tXwVq-h0R1rkygqwWCnQ39udqKuQa/view?usp=sharing