At one time I had both in my studio and they compliment each other very well. I would have to go with the JD800, it's one of my all time favorite synths and I miss it a lot, unfortunately I just don't have room for such a huge beast.
The JD is easy to coax new sounds from, just moving the sliders and choosing a sawtooth makes it a joy to work with and it's also a lot of fun.
I think you will get a broader pallette to create new sounds which can still be fresh today, the filters are nearly as good as sex to my ears and you can make lush pads, atmospherics, clangy belltones and much more.
Moog Voyager Roland D50 Ensoniq VFX-SD, Korg Wavestation Emulator II, Emax SE Plus, Korg King Korg, Korg Arp Odyssey(Whiteface), Minibrute, Takamine Acoustic Peavey Falcon electric