To the untrained eye, there may not be any difference between the Slav and the Asian one. But if you look closely the Slav squat has the legs spread wider and toes pointing quite a bit outwards as compared to the Asian squat
It's just the matter of what are you doing with your hands - if you want to pick up something from the ground then narrow knees will block your arms from reaching in front of you, but if you are holding something close to your face then narrow knees are better as you can rest your upper arms on them.