Quote Originally Posted by Ze_ro View Post
Well, Street Fighter Alpha 2 on the SNES used compressed graphics... but that needed a special chip in the cartridge, and had load times here and there.
Which is kinda of ridiculous, as just more rom would have been cheaper (or at minimum the same price but less complexity). A few later gen SNES used that setup, but I think it was more of an anti-piracy thing more than anything else.

As for sound quality... why not compare the sound dumps? I'm not very knowledgeable about the video game sound scene... but seems like comparing the .gym and .spc would be the easiest way to answer these questions.
Too many variables between the formats. One is a log register format, while the other is a block of code/sample/data from the original. Neither are going to be exact representations of how much music/sample data is used on the cart (though the SPC format would be closer for speculation, but there's still a lot of redundant data).