I've had the same experience, I also didn't feel any difference in the drive when putting on my winter Sottozero tires (happy on how they have performed so far).I've had both runflats and non runflats on my R55. The original Continental RF tires were hard and not too sporty. I replaced those with Hankook and then Bridgestone non RF. This resulted in much improved ride and handling. Since I had the room for a spare tire using regular tires didn't phase me much and indeed I never used the spare. The spare was just peace of mind. However in the winter I used RF since the idea of changing tires at the side of the slushy, dirty road in the cold winter was very unappealing. My overall opinion of RF tires wasn't that great.
Now I drive a F56. There is no room for spare or the tools needed to change a tire. When I bought the car I thought I would swap the tires to non RF (the car came with Pirelli Cintaturo) and rely on roadside assistance if needed. But after almost 10,000 kms with the car I have to say these tires are a vast improvement over previous runflats. I have heard that the F56's suspension has been tuned for RFs and this could be a factor, but whatever the reasons, I find the handling and road feel to be very good. I also have Pirelli Sottozero RF for the winter and I like those a lot too. So my opinion of RF has changed.
Oost
Cheers.
