New tyres can be deceptive as the rubber has not been compacted by the weight of the car for any length of time and the tread blocks are at their deepest giving a sense of much lighter steering / improved ride.
I've had Conti's 3/5, Goodyear Assy, Toyo T1R, Mich PS2's, Uniroyal RainSport 2's and Dunlop Sport Maxx over my 7 years of S3 ownership.
I'd rate Michelin PS2 best for outright grip in dry, but they drone on grey cement motorway road surface really badly (PS3's supposed to be better for this)
Goodyear I found to be best all-rounder, very competent in most situation, good on lack of noise intrusion
Uniroyal best for wet weather cornering / grip
Toyos, not really great at anything
Conti's gave poor wear rate, high noise, and didn't seem exceptional at anything
Only had Dunlops for 1000 miles before I put RS3 rims on, but they were generally good all rounder
If I had to buy today I'd buy Goodyear followed by Mich PS3 followed by Dunlop SM