QA1 are twin tube shocks which are steps below a high pressure gas monotube. Monotubes tend to ride much better as well.

The bilstein is a monotube design as well as the edelbrock. I agree the edelbrocks have some weird valving, but I wonder if the failure was from the one size fits all, as were the correct lenght (more likely).

The high pressure gas just helps the oil to stay stable during the heat of the action.