I run Vredestein Wintrac Xtream on both my RS3 and TT, just brilliant. Not wanting to overspend on the A1 (front-wheel drive) I fitted TOYO Snowprox, again superb. On my 8L S3 I had Sottozero. I've always been a winter rubber fan.
Whatever you choose will provide improved/safer braking and traction.
Summer rubber below 7deg C is a no no.
I wouldn't drive on summer rubber at them ambient temperatures and for sure I wouldn't let my wife; you choose.
And they save your summer rubber use. And, when you sell the RS3, you can sell 'em on. Not rocket science, if you know what I mean...
For the record: purchase BLUEY in October 2011. Purchased a set of OEM rotor wheels an Vredestein winter rubber the same month. 6-years on and still using the same winter wheels and tyres (and they are still saleable).
Do you get my safety/economic drift...
ALL my cars have winter/summer rubber, tis the only contact they (I/we) have with terra firma.
Same as there's 100s of professional roadtesters who LOVE the Audi RS3, or maybe not.
What suits one doesn't suit all, pays yer money and takes yer choice; I did/have and am 100% content with the Vredesteins - purchased in 2011 - and from the wear rate reckon they'll do a few more years yet. Keeping the RS3 for 10-years and I'm thinking they'll do 4-more winters.