I haven't done testing with a 2-1/2" barrel in the .44 Magnum. But I have with a 4" and a 7-1/2" barrel, using identical loads, the 4" barrel averaged velocities around 100 FPS slower than the 7-1/2".
(4" was an S&W 29, and the 7-1/2" was a Ruger SBH.)