I tried both units extensively and i find that the Aimpoint are a much better solution due to the ability to adjust brightness and also the longer battery life. the unit it self are not M4 compatible at the time of my test so you can mount a minidot and use it to the exact 2.6 inch over bore like the rest of the red ot, but it is an excellent platform for your MP5, Shotgun, UMP, and supplement to your scoped rifle.
the Leupold is a nice alternative, but the battery life is not as desireable, and if you go in and out of buildings or even from sun light to shaded area, I had a split second time that readjust and reacquire the reticle. this might be my eyes, but from lited retiel to just plane black etch reticle, my eyes took a second to realize this. something to consider but nothing of concern.
the Leupold optic are bright and beautiful, much better then the Aimpoint glass.
I did however find a little flew with the Aimpoint, the smallish tube makes a bit slower then using the larger tube or even the single pane heads up type. I had a little slowewr time on my shotgun compare to like a ML2 or an EOTEch. you just had to get the gun up to the exact right position to get that dot to show up, not as quick on a snap shot with a little distance.