The Wittelsbachs in their prime tried too much everywhere, and lost.Besides the Wittelsbachs had fairly large and wealthy holdings throughout history and what did they ever do with it? The Hohenzollerns were given a sandbox and a slice of the Baltic and they seized power by the throat.
The Wittelsbachs are a bunch of under achieving losers.
The Hohenzollerns took a longer route to their prime, but when they got there they tried too much everywhere, and lost.
Anyhow... Prussia is probably getting the Rhine because noone else is a proper custodian - Bavaria is at least a little suspect, Hannover is British so everyone else wants them NOT there, a local power is too weak to hold France off, and I suspect the Netherlands are a mix of too scary to Britain if they ever become a major power and too suspect given their long tendency to swing between republicanism and monarchy (rather than the firm staunch monarchism of Prussia; plus they already got Belgium). Austria might've worked if they wanted it, but then if they wanted it they'd have kept Belgium instead.