Currently driving a 2004 Audi RS6 that I love...

Looking for an RS7 or a S8 to use as a DD, my mechanic asks every time I service the RS6 if he can buy it, so the wheels are turning in my head. What is the general consensus here on S8 VS RS7.

S8 pros & cons as I see them: I admit I love the interior & exterior styling & looks of the S8 and it's supposed to be a special under rated top of the line engine factory freak gift from Audi that rates well above 520 stock flywheel hp, on the other hand it seems like a very large car and the back seats apparently do not fold down. Pre-owned S8 prices on average seem to be about 6-8K less than RS7

RS7 is the new beast for the US market, has sporty interior and 560 stock flywheel hp that can be juiced nicely. I do not love the back of this cars hatch design from a looks perspective however I feel it may be practical and useful. I have a friend who has an S7 and loves it.

Does anyone know of the common issues each of the cars listed above have or share and what to look for option wise etc?
What say the AUDI experts on here how to pass the torch to the next generation of Audi top of the line product?
TIA