Why Turbo?
 

I have just spent a lot of time reading about the turbo failures on the S6 C7, most owners are now starting to expect it. Now that the A6 C8 has a turbo it concerns me as to whether the change is a smart move or is it just Audi turbos that have this distinction as most manufacturers use turbos and do not have such a bad track record. To move from 333 HP to 335 seems like a great step sideways so I must think that it's an economic move and not one to improve the car.

1 turbo vs 2, higher strung V8 that people often mod, vs a single turbo V6 that most owners won't

it's pretty apples to apples.

FWIW, my single turbo A4 daily beater just turned 154k miles yesterday. Original turbo.

By "change" I assume you mean form supercharger to turbo - right? One answer might be flatter torque curve IMO.

The other reason is performance. Superchargers are driven off the engine with a belt so they drain (slightly) HP. That is offset by the boost they provide, but still parasitic to HP going to the wheels

Add to that the new A6/A7 have the 48v battery that means an alternator is not also draining HP

So the battery pulls energy out of thin air? What happened to the fact that “energy cannot be created or destroyed”. Not the mention the added weight of the battery and associated systems to support it.
Superchargers are preferred because of the lack of response time to utilize their attributes, turbos are preferred by the manufacturers because they are cheaper.

I agree with you I prefer the engine response of the supercharger. I wish my S6 had a supercharged V8 but oh well. I think the two main reasons for the switch in the C8 are the usual suspects fuel economy and emissions. Turbos do better in both cases on the government tests. If they are in fact cheaper to build that’s just an added bonus for Audi. Also in the C8 it allows for simplification to pop in the near identical twin turbo six into the upcoming S6. Makes it less “special” imho but easier/ cheaper to manufacture I’m sure. My personal opinion is a turbo motor takes more maintenance and care that many do not follow...and unfortunately following manufacturers recommended intervals is not good enough, but you are right in saying how do so many other manufacturers get away with mass market turbo motors with relatively few issues. Maybe they use “better” quality turbos. IDK Maybe we’ll see when/if I run into issues with mine. :(

I’m not an expert on how it works, but this is from a technical review I read on the new system

“This powertrain represents a significant change from the first generation, and not just because the old model employed a supercharger and a conventional eight-speed torque-converter cogswapper. The new A7 also has a 48-volt mild hybrid system, which not only works as an alternator and operates the stop/start function for fuel savings, it also allows for the recovery of up to 16 horsepower via regenerative braking.”

Interesting information but the stop/start is different in the US than in the EU and a lot of people do not like stop/start at all and they frequently turn it off or bypass its default on mode.
The Acura RL SH-AWD uses a battery for power enhancement, as do other manufacturers, so a substantial boost in power is available. I would have preferred this route for the Audi. (Not to mention that the Acura system has the smartest/best AWD system).

I don't disagree with you. I would have preferred that Audi take the same approach as Mercedes and how they use the 48v system to help provide initial power before the turbo spools up. Seems like a better use of the system.

That said Car and Driver's compare of the new A7 and the new CLS showed same 0-60 times

Besides the above benefits mentioned, the new turbo is electrically started. It winds up from 0 to 70,000RPM in 1/2 second... I think this is the way to go for future turbos and obviously Audi thinks so too. Response time is under 250 milliseconds.