Actually, thinking about it, the comparison makes absolute sense. The king of sports saloon is/was the M5. And both motors make around the same power, only how they make it is different. I'd like a screaming V10 as much as an S/Ced V8. As for the gearboxes, an auto behind a screaming V10 would seem odd, so a robotised sequential manual was the right decision. Unfortunately, robotised manual gearboxes are only as good as the programming logic behind it. BMW wanted it to give lightning fast shifts, and sometimes, it's compromised for normal driving.
Now that you've brought up the RS4, it's surprising how short the RS4 mania has lasted. I would've thought that a car being such a big departure for Audi would've kept people talking for longer, but it doesn't seem so. Maybe it's got something to do with the limited production?