<slightly off topic>
I don't know how different it could really sound but I can imagine there will be some differences that may increase if you change amps (as Chris Squire did with his rick'o'sound spliting bridge PU to a guitar amp) or just spread cabs away (since you'll be hearing different tone on each ear).
when my kit was at its peak, my main player was series II 5-string (other series basses starring in supporting roles). it was stereo'd from the DS-5 into an F2-B which then drove a stereo mesa boogie tube amp. The neck pickup channel went to an 18" bag end speaker, the bridge pickup channel went to a 2 x 10 sealed enclosure (a peavey, i think). i dimed the tone controls on the bass, tweaked the volumes to give me a good balance and used no effects. The optimal stage setup consisted of separating the speakers a foot or so. standing in front of it yielded a sound that would make the hair on the back of your neck stand up. it took a lot of trial and error to get things voiced to my liking. it was definitely not an easy rig to schlep around. for smaller stages, i would stack the speakers which greatly diminished the effect. i never met an FOH guy who could get it right, i usually went mono to the PA. so only my bandmates and i (mostly I) could bask in the sonic splendor that rig produced.
so, if you've the parts to make stereo play for you, it's definitely worth it. better get a hand truck or hire some roadies to move it around, tho...
