I would agree with Dicky, the best experiences largely come from having a friendly and engaging crew. My best experience was coming back from Dubai a few months ago. It just so happened to be on an A330, and I wouldn't say the cabin layout had much of an influence on my experience.
The A333s and B789s have a near identical layout. The A340s are a little long in the tooth these days but I like the bar layout, and if you have good service it can more than make up for the older cabin. The B747s as Dicky says is a very unique experience though, sitting in the nose of a 747 is quite a novelty but with such a small cabin (14 seats), finding two reward seats in Upper will require some perseverance and date flexibility, but it is doable especially in low season. The A332s are undergoing a new cabin refurb and the new VS layout has not done a commercial flight yet so nobody can say.
My honest opinion though is that if Upper flights are going to be a rare thing for you I would not book a flight based on aircraft type. It is
always subject to change, particularly on routes like NYC where there is a myriad of different aircraft types in use. If you want to minimise the risk you can pick something like LGW-MCO which is traditionally a 747, or LHR-LAX/PVG/HKG/DEL/JNB which is traditionally a 789 these days. But again there is never a guarantee that you will fly a certain type.
My advise would be to choose where to go based on well, the destination!
