Am I wrong in saying that the Neo Geo CDZ doesn't have a 2X CDROM drive but a larger amount of cache and just more efficient? I've had both top loaders and the CDZ is definitely faster but not twice as fast.
Here's a comparison of a CDZ's load times to that of a PS1 for KOF 99. On the PS1 it is noticeably faster especially the first round
https://www.youtube.com/watch?v=diBSihK56xE