Yes, the shorter the primaries, the better throttle response generally. Short primaries will make more torque above the torque peak of 5,200 rpm. The stock NA2 headers were designed for this purpose. However, the overall airflow of the header also makes a difference, and the aftermarket units tends to move more air overall compared to the NA2. That's why they show a bit more power over the entire curve.
There really is no BEST header. I guess what I'm trying to say is that it depends on your design goal. If you are a street driver who values torque, get a long tube header. If you track the car and would rather it feel like it's pulling stronger and stronger to the redline, a shorter header is a better choice. The NA2 are great on their own, but you can do a little better with aftermarket.
