I've flown several flights on B777-200/-200ERs, A330-200/300 and A340-300 - overall favorite: A340-300.
First of all, it's the quietest amongst all of them, and for me - as a passenger - that's, next to seat comfort, the main point. As for seat comfort - I prefer the 8-abreast seating over 9- or 10-abreast, just as much as the 6-abreast in C-Class over 7-abreast, so the choice there's easy.
Regarding comfort, well, I'm just under 1.9m tall, but have never hit my head on either of the planes, and the greater distance to the overhead bins does nothing for me, so, for me, I don't see any advantage in the interior design of the B777s.
Regarding takeoff performance, ok, the A340-300 is rather slow compared to the B777 or A330, but so what? It gets the job done, and gets it done safely. That's what matters.
Given the choice between any of these or a B767, B747, A310 or MD11, I'd take the A330/A340/B777 - but, as mentioned above, if my choice is from within this group, and flying my favorite will not make me have to pay more, or wait more than 15 minutes longer at any airport along my routing, then I'll take the A340.
On the other hand... as long as it has wings, engines, the name of a decent airline on the outside, the name of a plane manufacturer I trust on there as well, then I'll fly on it.
Smile - it confuses people!