I checked my ripped copy of CT PSX, it's 522 MB. The bulk of it is movies. They also have larger versions of the music and sounds, presumably better quality. There's also a copy of the JP ROM that's used for looking up some data.
Chrono Trigger's data is less than 4 MB, but the chip its on is 4MB, so garbage data is included in that 4MB. Some is at the end, some is in the middle.
...Ok, why is MONSTER.DAT 23 MB? I think I'll poke around that one a little tomorrow.