Very few reasons, if any. The dof and edge clarity are better in the 4-32, parallax is just a bit less finicky. Eyebox is pretty close. I have run both quite a bit, and I own 2x of the 4-32 models. As long as you have your comb height set correctly, the eyebox issue, well isn't an issue at all. I've been pretty happy with both mine. The 4-32 runs very well in the 7-26 power range, the 2.5-20 runs well 4-17 or so. So keep that in mind. 1 of my 4-32x50 is a ffp, and other is sfp. I will say the sfp model is much easier to use at 4-6x as reticle is MUCH more visible.