From a Glock 19 to a Beretta 92FS, I'd expect a difference of about 30-35 fps. I would guess that the G19 makes about 15-20 fps more than a standard 4" barrel, due to polygonal barreling. Subtracting that from the estimated 50... 30-35.
Others may provide more clarity.
Currently Own: Beretta PX4 9mm, Glock 23 (Gen 4), Glock 19 (Gen 4) x2