We purchased a set of winter tyres for the wifes fiat 500 when we got it over 3yrs ago. Its worked out very well for us tbh.
The original tyres are looking hardly used (18,000mls on the clock) and the winters are still fresh so from a wear POV it works. Makes sense really, half the wear and the right rubber for the occassion too.
I have been on plenty of test tracks where they replicate winter driving conditions like rain, ice & snow and i have driven vehicles with all the traction aids under the sun. Winter tyres always made a sizeable difference.
I dont agree with running them all year round as they do seem to give noticable increased tyre noise and i dont believe in the summer they will last so well, however by the end of this month i reckon we will have them back on.