I had 215/60R15 RE950 on my 400E for half a year, 10K kms on them. Before this I had stock size Michelins as summer tires, I remember I could chirp those small tires even at 60 kmph.
I use 215/60 Arctic Alpines on 15 inch wheels in winter, I know narrower tires perform better in snow, but stock 195 tires are just too small for a V8 3600 lbs sedan. I felt dry road performance was more desperately needed than snow traction even in winter, so I went with 215. The wide Arctic Alpines performed acceptably in snow, but certainly 205s would do a little better.
99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.