My bet is that the difference isn't the mechanical accuracy of the gun. I'm thinking one just fits you differently. I have to make all kinds of changes to the P-09, P-07 just because my fingers are so long. The distance to the trigger is too short on the P-09 for me to get my trigger finger placement correct and get a good grip on the flat sided grips. I don't have that problem with a 97 or 75 steel gun.
Perhaps you are at the other end of the spectrum--small hands or short fingers, so the short reach to the P-09 suits you better out of the box. If so, maybe some thinner grips or shorter trigger reach is what you need to get the guns to an apples to apples comparison. Just a thought, based on trying to "equalize" several different frames and seeing how my results change when I get the gun to fit my hands.
I'm not surprised you had good results with the P-09. It is still by far the best full size polymer gun available, in my opinion. But I, too, would love to have a TSO and will get one some day. I want a full size P-10 first, however. I'll have to buy some more Sugru and JB-Weld when I get the full size P-10, however. I already know that for sure.
Joe