Tokyo is the definitive version of the attraction. Now if only they'd go back to the old lap bars and seating configuration from 10 years ago (not that those were anything great, but the pictures and reports of the new individual lap bars and tiny seats don't look promising to me...).
The WDW version, for me, is the best compromise of ride quality and comparative comfort.
But it's really kind of sad that Splash is one of the only attractions that seemed to definitively get better each time they built it.