All weather tyres are compromise tyres that can be used all year around. They will never be as good as a summer tyre in summer time in terms of performance as the summer tyre has been optimized for only that season. If you want to get the best performance out of your car, you are better off with a summer tyre.
During the winter, it is also always safer to have a specialized winter tyre, especially if you have really harsh winters. If you want the best combination of best safety and performance during the winter, you are better off with a winter tyres. So best is to have two sets of tyres, but you can often manage with a set of all-weather tyres if your winters are not too extreme.