Pcp tuning???? Any guru's

[scoot]

So,,,, I'm messing about with my fx dreamline tactical. It has adjustment for reg pressure,transfer port and hammer spring. I've played around with the hammer spring wheel and transfer port wheel plenty, reg I've left at factory pressure.(approx 130bar)
So when chronoing and setting up for a certain velocity/accuracy,etc there are obvious overlap points. As an example:
lowest transfer port setting and highest hammer spring setting yields around 640fps
But.......
Highest transfer port setting and lowest hammer spring setting also yeilds around 640fps
Assuming a desired velocity is obtained with good accuracy and s.d. which method is "better". Should I use transfer port to gain velocity or more hammer spring and why?????
Thanks in advance for anyone who can shed some light on what seems more complicated each time I think about it.

P.s. I'm not trying to just screw the max power out of it.