Actually I'm fairly well versed as to the differences. I just want his explanation on the statement. The only advantage I see is that with an AWD car you don't have to get out of your vehicle to lock the hubs (if your vehicle isn't equiped with autolocking hubs) and you don't have to actually switch the vehicle into 4WD. AWD is always there. As far as actual performance in the snow, well I am still waiting for his explanation.
Resurrection of a dead post, anyways thought i would enlighten.
There isnt really any way to say that AWD is better than 4wd as it is going to utterly depend on the AWD/4wd system. Generally most 4wd trucks do not have any kind of locker or limited slip in the front differential. Most 4wd cars do have at least a LS in the rear diff. A transfer case found in a 4wd will transfer power at a 50/50 rate front/rear when it is engaged.
Most AWD systems have LS in rear as well, sometimes in front, and most of the time in the center diff as well. Newer AWD systems also have the ability to sense for wheel slip and route power to other wheels, this is a capability that 4wd systems typically do not have.
AWD has this advantage over 4wd, though typically 4wd are going to have better ground clearance. All depends on the situation. Most city driving situations, the ground clearence provided by a car will be more than sufficient. I did actually run into an issue getting high centered in the S4, but then again it is a bit lower than regular cars. Either way, hope this helps.