I will point out, that this argument is like the age old argument between manual and automatic drivers. Everyone will defend their choices to death because it's what they drive, and will never acknowledge that the other side is correct.
I happen to drive two very different cars, one for daily and one for track, but both see some quality time on the track as well. Both cars weight about the same (3,150 is the official quoted spec from the factory), both cars make roughly the same HP (330hp/268ft-lbs for the RWD, "305hp/296ft-lbs" in ricer math for the AWD), both cars share similar suspension design (MacStrut up front, 5 link rear), and both cars have similar torsional rigidity numbers (32,000Nm for the RWD, 28,500 for the AWD). I'm only saying this because I know I'll get a ton of flack from both camps for what I'm about to say, so I'm "qualifying" it with a little background...
Anyone who thinks one system is better than the other in any situation is smoking crack.
There. I said it. I'm going to take a step further on this argument and say that this is like the Special Olympics because everyone is a winner in this argument in their own minds. The truth of the matter is, there is no clear winner in this debate in that the AWD system doesn't really offer a real traction benefit until you've reached a certain HP plateau. Those that say, well, if AWD doesn't offer any true performance benefits, then why was it banned when Audi used it in racing? The operative word here is RACING. Where grip levels are low for the type of racing it was designed for and the engine makes plenty of power to overcome grip solely to the rear wheels. Therefore a AWD system in a high HP application for low grip situations is ideal. On the flip side of the coin, very few cars make 450+ at the crank. And even at that, on dry pavement 450+ HP won't be breaking traction all the time unless you drive like a total f**ktard. True benefit of using an AWD type system where power can be split to multiple axels only comes in handy on high grip situations when you can easily exceed 500hp. Otherwise any additional hardware is all going to add weight.
There. I said it again. Using hardware designed and applied to RACING as example of how one or the other is superior in a street car application is like, well, arguing about which Princess Leia is hotter. However, I will point this out to you using simple logic that actually makes sense. In the upper echelon of racing, where GRIP is king, RWD dominate because if you have more grip than you have power majority of the time, the add weight to split power up to the front is a penalty. RWD is the ideal layout here. In the upper echelons of racing, where little grip is available, like rally racing, AWD dominate because you need to maximize the use of power to the available grip.
In my experience of using both the RWD platform and AWD platform for track, I can honestly say that given the choice I'll probably take the RWD to the track more, but not for the chassis format, but the RWD is already equipped with R-comps and well, it's the BMW and I am driving it to BMW CCA events. However, I'll likely take the AWD to local autocrosses because it's ability to split power to the front seems to make it easier to navigate the much tighter course and frankly? It's far more comfortable in the wagon than the small 2 seat coupe. But I will say this. I took the AWD (okay, let's stop the pretenses here. '09 WRX wagon with some minor engine mods) to Buttonwillow in April when it's try, and then returned to Buttonwillow again in June in the RWD (MZ4 Coupe). In between the two events I took the WRX Wagon to Laguna Seca (it was WET). At Buttonwillow when the conditions were favorable (dry both times), the MZ4 Coupe was the superior car even if it had been in stock form on street tires (I've been to BW hundreds of times in the MZ4 Coupe in stock form on street tires). At Laguna Seca when it was wet? The WRX was churning out quick laps after quick laps despite the mixed conditions (it was pouring at one end of the track, turn 11, and bone dry at turn 5).
But anyone saying that AWD doesn't have performance roots or advantages? You're wrong. And anyone saying that AWD is superior to RWD in performance? You're wrong too. At the end of the day? You're all wrong. I'm right.