Believe it or not, I actually have the Roland JP8000, JP8080, SH-201, and SH-01 synthesizers. If I had to only have ONE and only ONE I would definitely get the JP8000 for all kinds of reasons that many people may differ with. For sounds I temporarily had the SH-01 Gaia replacing my JP8000 in my live setup, but due to lack of keyboard splits, rps, better phrase recording, plus a few other things, I had to swap it back to the JP8000. I now just add the SH-01 whenever I need a special sound and if I have the space to take it along. Actually, the JP-8080 and SH-01 have been a good combo that I've been thinking about using lately.
I have no idea which synth is "better", but for me personally I like the JP8000 the best and will never sell it. Probably one of the things that I like the most about the JP8000 is the functionality. I feel that while the sound "might" have improved with the SH-01 Gaia for example, the functionality has declined for my purposes. The SH-201 was a step in the right direction with regards to functionality and software, but missed the boat a bit in the looks (ergonomics) and perhaps sound department. The JP-8080 is simply awesome, but you need a keyboard of course to make that sing and you're also missing some key controller functions like the ribbon controller from the JP-8000 which I love. Again, it always leads me back to the Roland JP-8000, but that's just me.
Thanks!
Jim