I had the Alcantara seats in my 2013 RS5 and I really liked them. Besides what you mentioned that they don't get hot/cold, they also hold you in place better around corners. Less likely that you slide around, but that also made them a little tougher to adjust position in the seat as my pants didn't slide easily on them. As far as dirt goes, Alcantara or similar microfiber materials are the easiest to clean. I read a lot about folks advising against Alcantara because supposedly it gets dirty or wears. It's all a bunch of nonsense really. All you need is to damp a cloth in soapy water and wipe them down. Don't soak the material. Just keep the cloth damp, and then dry it with a dry cloth. Even steering wheels that get the oils from holding them, can easily be cleaned with soapy water. Just do it regularly before it's all disgusting, but even then it can still be cleaned. After cleaning and drying, use a toothbrush to make the fibers stand up again. Will look like new afterwards.
Regarding leather quality, the A models have the lowest quality leather. If you want Nappa leather you have to move up to the S at least or go for the Audi Individual program. Regardless, with the Alcantara seats the side bolsters are still leather, but even in the S and RS models its a lower quality leather. That's probably the one thing that bothered me a bit about my RS5, but it wasn't really a big deal.
Ventilated seats are not available with Alcantara, because it requires the seat cushions to be perforated. I think Alcantara wouldn't hold up if it was perforated. You are less likely to get a sweaty back with Alcantara, though. It was one reason I chose Alcantara, because Audi didn't offer seat ventilation with the sport seats in the RS5. Only the comfort seats were available with ventilation.
I'm back in leather seats with my AMG now. I would have gotten DINAMICA, which is Mercedes' version of Alcantara if it had been available, but the C63S only comes with Nappa leather seats. Fortunately, starting with 2019 the seat ventilation became available in conjunction with the aggressive performance seats. I don't miss the Alcantara now thanks to the ventilation. I do have the full DINAMICA steering wheel and it looks like new after 13k miles. I only cleaned it once so far. I do wear driving gloves, though, when I hit up the canyons where my hands get sweaty, but I don't wear them during normal driving. I am somewhat obsessive about washing my hands, though, even before the COVID crisis, and never really got into my car w/o washing my hands beforehand. I really hate touching stuff with dirty hands.
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