"All seasons" tires suck! You canīt get a tire that is good on all friction and heat/cold levels. A winter tire is made so it is still has the right softness at very low tempertures, while a summer tire should stay stiff enuogh to manage very high temps.
Put a summer tire on in winter and it will be hard as plastic, put a winter tire on at summer and it will be soft as a bubble-gum. Not quite but you get my point, there is no good compromise there. So buy a all season tire if you are not planning to keep the car for long. But if you are planning to keep the car for a good while, invest in good winter and summer tires.
BTW donīt know wihat kinda climate you live in but here we get real winters and hot summers. So here itī* best with a diffrent tire for winter and summer
(sorry about my spelling)