XV3080 and older jv-modules use 32kHz sampling rate whereas the newer modules use 44.1kHz. However, that doesn't mean that 32kHz is worse. Most of the JV-card samples have been edited for use with 32kHz converters I guess and some people have reported that some of these expansion cards sound too crisp or even weird with the new modules. Anyway, I have not tested this so I cannot really say. Anyway, I don't hear anything missing in the sounds, it's smooth and beautiful.
Anyway, I have read many comments about the 3080 and that the converters which roland use in it are very good and all roland jv and xv-modules sound different. I bet that the new fantom modules are good too. They have sampling built in too but I don't need that. The 3080 can be expanded by 2 srx cards + 4 jv-cards. The new modules can be expanded by using only srx cards but there are more slots for them. Anyway, you can get most of the JV sounds too if you purchase the srx cards which are made of the jv samples as the ultimate keys is.