The PX4 slide safety is difficult to operate without slicing your thumb.
The best version of the PX4 is the "C" model, which stands for "Constant Action." The "F" version operates like the M9 (DA/SA with safety/decocker), the "G" version operates like the 92G (DA/SA with decocker only), the "C" model has no safety/decocker and has the same short, light trigger pull on each shot, and the "D" model has a heavy DAO pull on each shot.
Because the slide safety/decocker on the PX4 is such an unfortunate design, the only model in this series that is suitable for fast use without cutting up your hands is the Constant Action "C" model.
Unfortunately, Beretta seems to have discontinued the "C" model, or they only make it on special order. Too bad, as it has a better trigger action than the Glock.