Hi German, yet another Rennteamer from D'dorf
Maybe you should have given a hint regarding the so-called "winter" in our region for those Rennteamers who are not familiar with it. During a normal winter season we may have 5-10 days with snow. Most time temps are above freezing temps, but with a lot of rain (climate should be quite similar to the southern part of the British island).
Hence you almost never have your car equipped with the best suitable tires, unless you have your own pit stop team to change your tires every other day
For example with the actual warm temps (I had a nice spin with the top down last Sunday - 15*C) the winter tires have disadvantages in terms of braking power from higher speeds (Autobahn) - also they reach their limit at a spirited drive on winding country roads earlier compared to the summer rubber (less corner speed).
On the other hand summer tires have disadvantages in the wet at relatively low temps (let's say 4*C + pouring rain) -winter tires are less prone to aquaplaning (due their specific profile) and provide better grip in the cold due their softer compound.
I'd say it depends - if you have no second car with winter tires for these rare days with "real" winter weather (or if you like to enjoy a spin at the weekend in the sometimes snowy hills nearby like Bergisches Land / Eifel / Sauerland
) you may get the winter tires, otherwise
it's not worth the money and you get worse performance during the "warm winter" season.
Talking about money: the tires alone are no problem of course because you save the summer tires during the winter,
but you may need another set of rims (I paid 3,100 Euro for a set of 18" Cayman S rims + Pirelli winter tires to replace the 19" Carrera S summer set).
I only bit the bullet because the wifey (using our 987 S for the daily commute) "persuaded" me to get the winter tires (I'm sure it would have been less expensive just to take a taxi on the rare snow days).
Regarding tire brand: for obvious reasons I can't comment yet on the Pirelli's performance in the snow, but they gained top scores in a Sport Auto winter tires test, whereas the Michelins were not recommended
With warm weather the Pirelli winter tires are still O.K. IMO - allowing a spirited drive, but of course less grippy in the bends compared to the 19" summer tires.