My automotive comparison (its too fun not to join!):
D&D + AD&D = Stutz Bearcat, sure its an old car, but an awesome old car!
2e = Desoto, nothing flashy, a dependable family car.
3e = 4WD Pickup Truck with over-sized tires, V8 engine, KC headlamps, Roll bar, a winch up front - perhaps too many doodads, but still a man's vehicle.
4e = Mini Cooper, its got a prestige name, runs well and fun to drive, but beyond that, its just a tiny, little car.
Pathfinder = 4WD pickup, with an efficient V6 - back to a man's vehicle, but smarter.
GP