I've got pretty limited experience compared to most of the guys here, but I'll take a shot. So much of the sound signature of tube amps depends on operating points, tubes chosen, AGE of components . . . BUT
the biggest difference (to me) is headroom - PP is gonna have almost twice the output of a SE topolgy (about 10W vs. abotu 5W max), so theoritically, the SE will start distorting before the PP would all else being equal (speakers, source, etc . .)
thats doesnt make PP BETTER than SE . . just one of many differences. SE sounds a little more nimble to me, PP more 'beefy'. Hard to describe .. I'd recommend you snag a couple old console stereos (magnavox or zeniths are plentiful and CHEAP) - grab the amps, recap, replace any out of spec resistors, and compare a SE amp to a PP amp yourself.
I have a few of each, and like both