Quoted:
I got the N battery 552 because it is considerably shorter. The AA model is just too big.
Bill3508
View Quote
Too big in what way? The "N" version is 1" shorter.
I can see if you're mounting an EO Tech directly to the upper receiver, having the EO Tech 1" further forward doesn't hurt. But, if you are mounting the sight where it was to be mounted - as far forward as possible like on an FF RAS, the extra inch doesn't matter.
If you can mount the EO Tech on a FF RAS, I can't see why anyone would want to get the "N" version. AA batteries are easier to come buy and, as Yojimbo mentioned, the battery life is considerably better. The "N" version has an average battery life of 150 hours. You'll be buying far less batteries if you go with the AA model. That's why I chose it myself.
BTW, if you're using AA batteries, you should get lithium for maximum battery. They round $6 pr/$11 for 4 at Wally World.
[img]http://home.insightbb.com/~toneboy2000/images/04_ar15_001.jpg[/img]