Okay, I just dug back up the PSX versions I had played. I was wrong about a few things, so I'll just start over.
The first thing to know is that Capcom remixed a bunch of classic Megaman tunes for the two arcade games (which were only a few megabytes, but sounded much better than 8-bit NES).
When Capcom decided to port the NES games into single overpriced PSX games, they included the remixed tunes. If you hold in "select" when selecting the Navi Mode, the game will use any available remake instead of the classic tunes. However, there weren't enough remakes to cover the entire games. Like, for example, Bombman's stage doesn't have any remixed music.
The remixes sound better than I remember, but they still feel out of place among all the 8-bit graphics. And it's only made worse by the constant swapping back to the original tunes when there isn't a replacement available for something.
The PSX games all seem to weigh in at about 300-400 megabytes each. When looking at the contents of the disk in my PC, about 90% of that is taken up by the remixed musics, 10% is taken up by the unlockable image galleries, with less than 1% making up the actual game. That is clearly a blatant abuse of space. But, I guess Capcom didn't care, because they were already wasting the entire CDs on several-kilobyte games.
Considering that Megaman 8 is reportedly the Sony-censored PSX version, instead of the superior Sega Saturn version, I would say that the first six games, and Megaman 8, are all being run off a PSX emulator (or they just used some cut-rate "PSX to PS2/GCN" port generating system).
Considering that the PSX games were all around 350 megabytes, you can multiply that by seven. I'm guessing the PSX games in this collection took up a little over two gigabytes. Add a few megabytes for the SNES game and two arcade games, and you've got the reason why the GameCube version was boned by Capcom. The GameCube disks are 1.5 gigs. The PS2 DVDs are 4.5 gigs. This collection they slapped together is maybe 2.5 gigs.
Instead of fixing the horribly-bloated audio (or making it a two-disk game), they just chopped the remixed audio from the GameCube version. Suddenly the game is less than half a gigabyte.
By the way, the PSX versions let you fully customize the button layout in the options menu. I had planned to get the GameCube version, and play it with a Nyko Playcube, which should have resulted in a control setup exactly equal to the default PSX version (which is as good as the NES originals, but with a more comfy ergonomic style), even without customizable buttons, but Capcom completely ruined that by forking with the "A & B" position.
Congrats Capcom! You just lost a sale! If anything, I might get the PS2 version. But really, why bother?
Oh yeah and, I had planned to get the GameCube version over the PS2 version in part because the "exclusive interview" sounded better than the "episode of the lame 80's cartoon series", but from what I've heard, the interview was produced for Capcom by "G4". I haven't seen any G4 myself (not available in Canada), but I've heard nothing but bad things about them. I'm not basing my version decision on that (my decision has already been made, by the cut audio, and forked-up controls), but I just thought I'd toss that out, for anyone who hasn't heard.
By the way, the PSX games had bonus PocketStation content (as if anyone has one of those things). How much does anyone want to bet that it has not been converted into GBA-connectivity content?