I'm exhasted and am at college typing this, so bear with me.
The JV1010 is a great module. You have the built in SESSION expansion board with great sounds, and if you've ever wanted a JV/XP unit for a real cheap price, then there it is. If you want to save money, so for it. The drums sets suck, but the session board will make up for it somewhat.
When you get extra cash, you could fill up the one expansion slot on the JV1010 with a board of your choice. I would recommend the SRJV80-10 Bass and Drums expansion board since it adds better bass and percussion, so good infact that if played properly will surely fool anyone.
The downside is that editing on the JV1010 is like a connundrum. It really can't be done. This is not a great live unit. Better use of it would be in the studio. A fabulous editor program is provided with it. You'd need a PC or MAC to take advantage. Once you use this program, you'd be in good hands.
The SC880 - This is a banging module. Best bang for the buck PERIOD - End of story. You don't have the deep programmability as you would on the JV, but you get over 1200 sounds, 43 drums kits, and the sounds are very good. Many of the osunds have been recycled from the JV series anyway.
The guitars rock, the drums are great, the Pianos and EPs are good too. You also get 5 independent effects processors, two midi inputs, and these can be assigned anyway you want them to.
The modules' dimensions are quite big. 1 rack space, but real lengthy in the deep department. It is very easy to get around on this module and all CC#, NRPN, etc. are supported on this module.
I have the Roland XP60 and the SC880 (like having a JV1010 and SC880) and find that they compliment each other very, very well. The best thing is to test these units out for yourself okay? Good luck.
The Infamous EPU.