I fly the A330, A340-300 and -600.
The sad fact is the A340-300 has a terrible Rate of Climb (compared to the other two). Its unfair to give to 'numbers' to compare as we fly them at such staggeringly different weights. (but to say that the -600 climbs at about 1.5-2 times the rate to the -300)
But some of these number may amuse you:
We took off in the -600 from HKG to LAX about 3 months ago at MAUW (368,000kgs) *the -600 rotates very slowly because of its length and the fact that you need to use 'Config 3' to help prevent a tail strike* Vr was 167kts.....but the main wheels didnt come off the ground until 192kts!