The techie explanation!!!
The swing of cricket ball is related to it aerodynamics and therefore will dependant on a number of factors. In this case the seam height and angle relative to the wind direction and also the atmospheric pressure and speed.
It occurs because of an air flow trip from laminar [smooth air] flow to turbulent [rough air] flow on one side of the ball, generally caused by the seam. Depending on those factors it can happen at various speeds, i.e with lifted seam, misshaped ball, rougher scuffed side just allows it happen at the medium pace range.
This transition in air flow create a pressure difference on one side of the ball. Think of it as more pressure on one side and less on the other side so it pushes the ball to the low pressure side and therefore causes the swing. [A bit like the dimpled golf ball stuff and why a dimpled golf ball will travell further then a smooth one]
so yep different types of balls will have an effect on swing.