Another reason for Republicans' higher level of sexual satisfaction could stem from their conservatism. Democrats are notoriously horny, whereas Republicans are traditionally uptight. In fact, Republican research facilities are working on ways to make the male climax actually painful, so that the noble act of procreation will be as unpleasant as possible.
Actually I made that part up.
Satisfaction is not an absolute measurement. If you get less, but want less, less is enough. If you always want more, when do you have enough?
Ask Republicans when they think they're rich enough. Waaaa hahahahahaha!