If you have a weak ignition system, buy Federal pistol primers. They are the most sensitive primer on the market. You are better off buying a new mainspring because a weak ignition system will degrade over time, but, still, I like Federal pistol primers for their sensitivity.
I have shot every brand of American primer over my chronographs and I am going to say, what I see varies. Primer composition is a mix of chemicals, the energy in the mix varies, the next batch of primer cake will be different. Then the primer manufacturers are free to change anything, so there is no guaranteed consistency in anything. Buy by price. Unless you want Federals. Then you will pay what the market wants.