I was close to getting an RS5 2+ years ago (sportback) but decided two wait a year or so for the G80 M3 to come out... It ended up being 2+ years specially that I want AWD but I'm so happy I waited. The RS5 is a very nice car but in my opinion it doesn't have the character of a BMW which is what most of us BMW fanboys expect. And of course there's the killer performance of the G8x
I noticed you're listing "cooled seats" as an advantage for the BMW. Keep in mind those are only ventilated seats (not really cooled) and I've heard mixed reviews on their effectiveness. I specc'd them in my car because I think they'll help but I don't expect them to be a game changer...
It appears the RS5 will work well for you but I strongly recommend you take one out for a test drive.