economy seat choice

Does anyone have suggestions re: leg room on economy on flights in and out of boston? Is there a difference between the 747-400 and the airbus-300 or 600 in terms of there being more leg room in the 61-64 side seats?
Any idea which are the most likely planes to be in service on the boston route over the xmas hols?
many thanks

[Pete]

Impossible to say which Aircraft will be on with any certainty, although stats suggest it'll be a 747. That's a good option for the back of the aircraft, since the curvature down the back gives you a bit more room that the Airbus.

Pix.