There are several considerations that lead to aircraft preferences as suggested earlier.

Domestically in US, it's always a treat for me to fly on bigger aircrafts.

I always get excited if I see a 747 or 777 on the schedule. But since these birds are now rare, except on hub to hub flights, A320s (United) work fine for me.

Now, internationally on the premium cabins, nothing will beat the 747s for exclusivity. The 777s are also fine, which I would actually prefer if flying on Y.

The A340s are similarly comfortable. They tend to be newer and quiet in my limited experience.