imho, the best ride is in the front of the upper deck of the B747, it can get a bit choppy down the back in E-Zone, but nowhere near as bad as down the back end as in stretched airframes like the A340-600/B777-300.
In the A320 family, I far preferred the A321 to the A320 to the A319. The A321 had a larger aircraft feel in turbulence, probably due to the higher wing loading, whereas the A319 just bounced all over the place - even in the flight deck!