I have both molds and for the same weight, the Freestyle is a much larger head, since the collar on the aspirin head is also included in the head weight.
I like both, but really depends on what I'm doing with them.
I'm usually using the Freestyle for plastic, but will use the aspirin head for tying and/or plastics.
You can put a much thinner plastic bait on the Freestyle, than you can the aspirin, as is for both, since the wire keeper doesn't need a fat bait to keep it on the hook. The Aspirin head, that lead barb tends to split baits if they're really thin.
I also pour the Freestyle now with only the WB800 style wires, and frankly anything that takes that style of wire. IMO the WB400 didn't hold plastics very well and that wire also didn't stay solid in many heads, and became loose too easily, so I went to the bigger wires and that's all I use.