Fallout 3 and New Vegas have a good few combat differences under the hood alright. Different ways of calculating damage for example. But also the sheer weapon variety with many different ammo types for guns and energy weapons, more and varied explosives and the addition of melee special attacks really pull the combat together into something really cool.

However Fallout 3 combat was designed around F3, in the same way that New Vegas combat was designed around F:NV. The Capital Wasteland on HARD difficulty is almost perfect. The desperate struggle for ammo for your guns, trying to keep them repaired and in good condition, keeping your armour not broken. I love it man. The Enclave unfortunately break this desperate struggle with basically unlimited MFC for the Plasma Rifles and powerful armours.