Re: AN/PVS-24 M2124 Clip-On Night Vision Device.
The 22s work fine, IMO. The 24 is a tad lighter, and smaller, but I think that's about it. From what I remember, I chose to use the 22 vs the 24 because I felt it was more robust and I didn't gain anything from using a 24. Same technology, just a few ounces saved I think. The 24 is meant for the M4, whereas the 22 is meant for a rifle.
-edit
The 22 on the M110 doesn't line up perfectly with the objective (height), but it never caused me any issues with shadowing or anything weird.