I was led to believe that the braking performance of winter tyres are inferior to summer tyres in the err… summer
In dry conditions, sure. But that’s where your braking performance is already at its best, and when visibility is best too. So what you’re doing is trading off a small amount of performance when you need it least, for a much larger amount of performance when it could save your neck.
I ran winter tyres all last summer, and sure there’s minor downsides but there were pluses as well- such as happilly driving through muddy fields (one memorable b-road diverstion spent half in ditches and verges dodging 4x4s who were afraid to put an inch offroad), and excellent grip in floods/standing water. I wouldn’t take them on a trackday though.