having grown up in AMG and all varieties of MB.
You will never find another vehicle that offers the enveloping feel an S class vehicle will offer. the S63 is amazing, the 4matic version currently makes it very appealing. Seats, the new command system etc etc...
While I don't own an RS, my S7 is nice, but not like S class nice. The S class is nice enough that you see enough people being driven in it. The RS/S7 - is less so.
There is a reason for that. The RS7/S7 is a very driver oriented car that also happens to be able to fit a lot of stuff in the car. If you are looking for a faster car (and cheaper) - the RS7 would fit the bill. Is it comfortable enough? absolutely, but it's not quite executed like the way the S class is.
I am only responding under the assumption you would be considering a current gen S class btw.
You wouldn't take the S63 to a track day...you could, but it's silly. That is NOT to say the RS7 is a real track car either, it isn't; but you can and would look less silly and would have way more fun.
Current gen S63 Command system is also better than the updated MMI in the 2016 RS7, and I have to say, there is nothing quite like seeing that AMG seal stamped into the center console leather.
I think both are exciting cars, but it really boils down to what is it you want to achieve: sport performance saloon (RS7) or a sporty saloon (S63)
also keep in mind, S63 has 3 rear seats, RS7 is 2+2. AMG exhaust note is more raw, but you won't hear much of it inside the cabin, RS7 is like a high pitch bark (F1 style), and you'll hear it for sure + the burble popping instills all sorts of giddy feelings.
I'm partial to the RS7 because well, i drive an S7. But having been in every S class iteration for the past 30 yers and driven daily the last few generations as a daily for awhile, I just have to say, that MB gets it right when it comes to comfort with a touch of sport.
Audi is refined performance.
BMW to me is like rabid dog with a muzzle.
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