I decided to get an EOTech for my AR but am stuck between two models, the 551 and the 552. The only difference between the two is the power source. The 551 has a small battery and the 552 has a AA battery. Which one has more pros than cons? Does the length really affect anything?

Any advice owners of either models have would be appreciated. Thanks.

I use all 552's because of the abundance of "AA" batteries. The length of the sight has never bothered me in any way...never affected anything on my rifles.

*You can stop in any store, gas station, rest stop and find "AA" batteries.

*"AA"'s are used in GPS units, many flashlights, radios and other various equipment as well.

*You can get them by the 100pack at COSTCO and SAM's Club...CHEAP [:)]

Don't forget battery life with the 552 is up to 500 hours of use, where as the 551 is rated at only about 100 hours of use.

I have two of each.  It really depends on your needs. if you need long battery life, the 552 is the way to go, as mentioned by the two members above, the battery is easy to find and you can get 500 hours from a regular AA batteries and approximately 800 hours from a Lithium.

If the rail space is at a preimium on your gun, then the 551 is the better choice.  Like on a M4 with Colt double heat shield handguard and a ARMS #40, you are better off with the 551 since you really don't have that much spaces.