After seeing this, I'm even more confused as to which will be my next purchase: SP-01, P-09...
A gross over-simplification would be...
The P09 is a polymer receiver, basically intended to reduce weight for those who
carry for a living. Comfortable to shoot because of the full-size, but still a reduced-weight pistol.
The SP01 is an all metal gun making it more comfortable for those who may
shoot for a living, e.g. a competition gun. In competition the added weight helps control recoil. And since the gun comes off when the competition is over, carry weight is not a primary issue.
That doesn't mean that SOME people might need to reverse the rolls.
At least that's my take.