Whats the difference here, I got some of both and Im not seeing any difference other then the obvious rib on the back, is one better then the other?

Using calipers with .001" accuracy I measured both types in the same places at a dozen spots and 10 out of 12 measurements were the same. One mag was blued and one was painted black so the thickness of the coat of paint could account for the 2 spots where the mesurements were different. The only real difference I could see is the way the back of the two halfs of  the mag were folded before being spot welded.

Like JA mentioned....It really boils down to tooling and a different way to stamp them out.  I've heard that the rib adds a little durability, but I've never had any problems out of any of my mags that are ribbed or non-ribbed.

I prefer the non-ribbed because they feel better in my hand when changing mags in and out.  It's just a personal preference.  I actually have more of the ribbed style.

I somewhat like the feel of them minus the rib myself, I was just wondering, thanks for the into.