Looks? It is in the eye of the beholder, not an objective assessment. Comfort? That depends on the internal amenities, which are airline selected option. Fuel efficiency? Now we have a bit of objectivity, although either aircraft are available with several engine choices, and in the case of the 767, a winglet kit is available that aims at improving fuel economy. But the 767-300ER was introduced in 1986 while the A330 first flew in 1992. A six years additional design time and improvement in systems and motorization is bound to procure an edge in fuel economy to the later airplane. Moreover, the Airbus cabin is a bit wider, accommodating an extra seat on each row. A wider plane with about 12% more passengers is thus more efficient in a seat/mile basis... provided the aircraft flies full, that is. As for the speed, the A330 cruising speed is Mach 0.82, a bit faster than the 0.80 of the 767.