Actually, those were suppose to be separate statements. Sorry. :)
A lot of cars (regardless of their transmission) couldn't navigate the hill due to lack of power.
4wd vehicles usually have an advantage of a 4L gear (4 wheel output, lower gear ratio).
Of vehicles of equal rear wheel horsepower (including overall gear ratio), they are equally drivable, if the driver of each knows how to operate his vehicle.
A slipping torque converter can be a significant cause of transmission overheating, so although it may seem like a momentary advantage, it's a long term (and expensive) disadvantage.