I'm a Motif ES and an arranger ( PA80 )owner. While Trance isn't my style of electronica per se, I do like other genres of synth oriented music.
The Motif ES phrase factory and the arps are excellent tools for electronic genres, and I can produce a lot faster using them than I can by making styles on my arranger.
The irony though is that the PA80 allows for deeper patch editing and I think it's better than the ES for actual sampled synth sounds.
You could save a ton of money and get something like Reason or FL studio and be ahead of the game. FL really lends itself well to creating any type of electronic music and it's tools are far advanced vs the Motif series, provided you have some ability to create patterns from scratch.
There are enough freeware synths out there that for little investment you can surpass sonically anything that any arranger or Rompler will do. There are many virtual analogs or analog / sample based / fm / hybrids that can be had for nothing, and these will often surpass any wave / sample based solution for making scratch or unique synth sounds.