I have a 2018 GLC 43 and live in Europe thus know about the slippery or icy conditions. I did not change over to winter tires this year as you need to buy new wheels and tires because no one make 21" winter tires. The winter was very light this year and could tell that we had summer tires. To the point; you are correct about the 4 matic+ on the 63 and 63s BUT I am a Very spirited driver and never lost confidence on cold roads with summer tires on our GLC43. It is definitely rear wheel drive biased and you can throw it around considerable if you want to...pretty fun really in my opinion. You can tell that it is all wheel drive on the road which I find confidence inspiring if you will. Not a perfect car but still a good and fun machine. Good luck.