I agree, I think you will be much more comfortable on an Airbus. Do you know which one it is? And who the airline is that you would travel with?

I've traveled on a 757 across the country with American Airlines and it was not very comfortable at all. I was definitely ready to get off it after 6 hours. Or after 1 for that matter. I haven't traveled on an Airbus A330/340 but have on the A380 and it is definitely more comfortable than a 757 or even the 747 I flew on. Good luck!