Yamaha MU100 and MU100R

Folks:
I am intending to purchase a Yamaha MU synth module, and am currently examining the MU100 and MU100R. I had assumed that since one of these is a full rack space, and the other a half-rack, but otherwise both share the same model numbers, the difference would be front-end controls and expansion slots. However, Yamaha's website indicates that the 100R has a lot more voices.

Does anybody have experience with either? Is there much difference in sounds between them? . . . in MIDI processing power? There's certainly a hefty difference in price!

------------------
It's really about music, isn't it?

MU100R is not just only a rack version of MU100, it has pre-installed two plugin boards: PLG100-VL and PLG100-VH, and MU100 only has a space for one board, you should purchase a plugin board yourself, but MU100R has done all of this.

I'm now using mu100R, For me, the plug-in boards in mu100R are the best two among other plug-in board series. Since VL board allow you to have additional 256 VL voices (which is total difference from the original XG voices). So you will get more sounds than mu100. In my opinion, mu100R gives you various sound combinations than mu100.

Check out the PLG150AN plugin board. It has some incredibly Phat sounds. Its modeled after the Prophet5.