MS2K is more for dirty gritty sounds,basically based on the MS20 most factory presets are aimed at techno heads(in the black version at least) lots of overdriven basses and deep sounds,plus your average synth sounds,clavs,rhodes pianos ,synth leads and the like,only thing lets it down is the polyphony!!only 4 voices which is pretty mean considering they made pads and string sounds too...Mod sequencer is great...arpeggio is basic(no editing of your own patterns)but no prob if your using ext sequencers
vocoders ok,not the best I've used quite a hands on synth and very capable synth with a little programming knowledge..
I've got the Black rack version..it was either this or the Microkorg....went for the big brother model MS2K
Never used an XV3080 probably more your run of the mill module like the 1080/2080 full of your universal sound set
I like my ms as its adds a little growl where other VA cant go
given your setup and the synths you have,I would say the MS would be more for you,theres more hands on control and ability to produce jarre like timbres with the MS,but if your after more traditional sounds then perhpas the XV3080 is more up your street
I have occasion to own only one of them... The prize is the same - 300 Euros... 
in XV3080 i have JV/XP/JD series + srjv expansions and srx
