AFAIK GC games in GCZ are compressed lossless where for the Wii they're 'lossy' (can't recreate the exact disc, wrong MD5sum is generated).
When Dolphin switched to VS2015, a seek-bug caused TWW and a Spongebob-Game to crash at a certain point, but, at least in TWW, it could be worked around by compressing it to GCZ. (It has been fixed of course)
As the game disk is compressed, it needs to be uncompressed on the fly, using only some CPU time that isn't very noticeable (execpt for Wii games).
Some games may not compress well (Zelda OOT, 1.36 GiB -> 1.28 GiB), but some might do; i once read that Animal Crossing in GCN can be compressed to about 60MiB (due to being a N64 game).. Also, NSMBWii can be compressed from 4GiB down to 366MiB
I couldn't find and instance of GCZ causing crashes (maybe Wii games?) or fixing some timing-bugs, so i guess for at least GC games, GCZ is good enough.
When Dolphin switched to VS2015, a seek-bug caused TWW and a Spongebob-Game to crash at a certain point, but, at least in TWW, it could be worked around by compressing it to GCZ. (It has been fixed of course)
As the game disk is compressed, it needs to be uncompressed on the fly, using only some CPU time that isn't very noticeable (execpt for Wii games).
Some games may not compress well (Zelda OOT, 1.36 GiB -> 1.28 GiB), but some might do; i once read that Animal Crossing in GCN can be compressed to about 60MiB (due to being a N64 game).. Also, NSMBWii can be compressed from 4GiB down to 366MiB
I couldn't find and instance of GCZ causing crashes (maybe Wii games?) or fixing some timing-bugs, so i guess for at least GC games, GCZ is good enough.