As both a frequent flyer and former US employee, I think that the A330 is a better experience for the following reasons:
- newer a/c and updated cabin
- electronically adjustable seats with 60" of pitch
- Sony Passport video/audio on demand
The 767 is still a nice ride, however the cabin is older, seats are slightly smaller (55" pitch) with manual controls for recline and legrest (that's about it; no lumbar, headrest, etc.), and small PTVs - most with scratched screens - showing scheduled programming.
Generally the service is better on the 767, since the f/a's tend to be more senior and like working the aircraft and serving only 23 passengers maximum. The A330 holds 35 in Envoy, plus 6 in First (which is now part of the Envoy cabin as far as meals and service are concerned). So, it takes longer for food, etc. and they are much more rushed and less personal in the service.