I am on my 3rd set of RE11 (265/285, 285/285, 285/285). My car is completely stock. There is no way I would consider running the 265 again as the 285 gave the car a much more balance feel. With the 265, my backend could barely kick out under power. With the 285, I find the car being able to go from understeer to oversteer with some throttle or steering input. It was nearly impossible to do it with the 265s. While the 285s felt much better, I can say the time difference is probably a few tenths at best. Still, the ability to drive the car the way I want it to is worth it alone. Also the 285 will make the car drive better in the long run as the fronts will wear less quick than the 265. (Yes the front made that much of a difference in how the rear drove)
As far as life, the 265/285 got about 200 runs and probably 7500 miles. The second set got about 180 runs but about 10K miles. My current set has about 12K miles on it and about 150 runs. They are almost past their prime, but I am holding on as long as I can before I buy new tires. I can tell you at 10K miles, these tires get extremely noisy. I currently have a 20 miles commute, I have to wear ear plugs as the car is unbearable in terms of noise. When they were new, they were definitely quieter than the RE050. RS3 and AD08 are comparable if not faster, but they don't come in the 285 35 19. They only come in 275 35 19, which is smaller in terms of overall diameter. 4 285 35 19 gives me a dead accurate speedo, the smaller tires won't. I also have to clear speed mountains here in California, so the bigger tire really helps with that.
As far as A6, I only did 2-3 events on them. It's funny that they feel like $hit in the course I ran them in, mainly because of the heat it had and the lot. I mean the A6 just didn't feel like it would turn, the car just understeer and plow where the RE11 would slide left and right and whenever I want. Yet when it came time to finish, I believe i was a second or something over my street tire run.
This was from last year. Tires were near the end of its life.