Depends on what you're going to use it for... If you just want an effect for live play, it's a matter of taste and ear, but if it's for digital recording, it's the J-Station - hands down, end of story.
AFAIK, it's the only one under around $600 with S/PDIF interface, above and beyond all else. This is make-or-break. No multiple A/D/D/A reconversions with S/PDIF, and that's important.
The computerized editing control via J-Edit is great, too. Otherwise, it's just an effect, which is why more people aren't enthusiastic about them; they're not using them as they were really intended to be used. If you haven't operated the J-Station via computer, you don't know ANYTHING about the unit.
It's not a cheap device. Having amortized their investment, the J-Station box has dropped from around $450 to under $150 for the same unit, the upgrades for which are downloadable firmware rather than expensive hardware.
And - lastly - the J-Station is American made.