Highspeed,
I own both in 40s&w, not 9mm, so here is my perspective.
96 beretta is utterly reliable, and has never once failed to feed, fire or eject in 3 years of shooting. Sharp recoil in full loads. Good accuracy and I like the safety decocker. Till I got a 10mm witness, it was my standard truck gun because of its reliability.
P9 Ultra (springfield armories cz75 clone in 40s&w) all steel, very mild recoil. Very accurate, good reliability (somewhat picky on lead reloads) and very solid. I like the DA and the SA cocked and locked for carry. Decided it was to nice and accurate of a gun to risk carring and only use it at the target range.
If I were to pick only one it would depend upon my reason. If it was to carry, get the beretta, reliable and accurate. If it was to shoot at a target range, P9, very accurate and beautiful trigger.