For some reason I have read in a few different places that the AK sight radius is what harms it's usefulness. It didn't seem much shorter to me than an AR15 carbine length sight radius, so I whipped out the camera and a measuring tape. I tried to line up the end of the tape with the rear apertures on both guns. While things may not be lined up exactly the same, it gives a decent idea of the length of sight radius between the two rifles. Both are look to be right near 15.25"

I think the advantage of the AR15 sight system is the proximity of the rear aperture to the shooter's eye, in addition to the peep style aperture. This allows the eye a larger area in which to center the front sight post, thereby allowing a more precise center. Sight radius doesn't seem to be the discrepancy, rather than the placement and style of sight.

All true.

I'd like to get a Tech Sights rear peep for the AK and do some measurements with it compared to a rifle length gas system on an AR.

I would have to say that most ARs being sold are carbine gas length sight radius, but I would also have to say that a large portion of shooters add some kind of optic.

I agree that the advantage goes to the AR sight system as the rear peep is closer to the eye. Before the tech sights were out, I welded rear peeps to my AK's receiver and I like it much better. I find the gun much easier to aim. That said, the ole Winchester and Marlin 30/30 lever guns sights are out front and lots of deer are taken with them.

The Tech Sights should make a big difference on the AK as to usefulness.  I know it did on my SKS.  It is a MUCH better shooter now.