i've blabbed about this before, but i recommend the Revo. if you buy used, you can likely pick one up closer to 200-250 more than a Mobius, and i think the inbuilt synth is worth that price. the circular sequencer took me a little while to get used to (it's not hard to input data -- it's just that one gets used to the typical left-to-right method of sequencing, and this clockwork style takes some adjustment), but now i love it.
besides price, i'd say the only other big benefit to the Mobius is space. i think its rectangular/rack design is much more efficient than the Revo. in fact, i wish Jered would just build the Revo into the Mobius and call it Revolution 3 (or whatever).