You are buying a new-to-you Z4 ? Hope you like it ! I recently shopped new tires for my 2006 3.0Si Coupe, and I agree, definitely not run-flats.
My car had older (seven years from manufacture) Goodyear Eagle Sports when I bought it, and they were better than expected in rain and dry - they had about half tread left. But a bent rim, and new rims of different size = new tire time. The US "uniform tire rating" numbers on wear for most of your choices will be in the "500+" range, but most of the warranties have fine print limiting your replacement mileage to half of the standard warranty if front and rear tires are different sizes (rear drive = expect you to burn up rear tires :wink: ).
My priorities were wet performance, dry performance, and noise. I chose Michelin PS4 AS's. Admittedly they are new versus the older Goodyears, but they are definitely quieter, and they stick better in the rain, which I was 'conveniently' able to test two days after installation. The Eagles are more 'square-shouldered' - i.e. their tread edges come closer to sidewall than does the PS4 AS tread. Conti DWS06's are even more 'round-shouldered' than the Michelins. The PS4 AS tires may not be as quiet as the PS4S and competitor summer-only tires, but the AS tires tend to last longer AND will handle Spring and Fall cold temps better where I live.
I made my choice from TireRack ratings, Z4 friend input (2006 Z4R), and price point (Michelin was between Bridgestone and Conti in price for my sizes). I like tires to last a while - but it's the one area I tend to 'splurge' on my vehicle care.
