My vote goes to the A340 over the B777. It's amazingly quiet and more stable I think than the latter. Actually even the A330 is even quieter than the 777.

Surprisingly the B747-400s' quietest zone is not in First Class or the upper deck, but actually right at the wing section. Some airlines have some of their Biz class there. I find this zone the most stable in any turbulence, quietest (the engines are below you and noise is blocked out by the wing), and the landing the smoothest since the main landing gear is also directly underneath you - thereby cushioning the main landing weight!

No 737s for me!