I've got the Oneway with both bowl and spindle. Wanted the bowl for use with long overhangs, as Jeff says, but found it's a great thing to have on larger diameter stuff and where you want to turn thin as well. Keeps you from getting into the centrifugal spread situation, which ends up with out-of-round or uneven thickness rims, even if you press a bit too much. Stabilizes against chatter on thin stuff, too.
If you do get the Oneway, get one of those ratcheting box wrenches for the bolt. Best way I've found to be able to work in and about almost any bowl configuration with minimum frustration.
I cannot fathom why they went with two over and one under on the spindle wheels, because I think most still cut above centerline on spindles, don't they?