I looked at a lot of different EOtechs. I would have gotten the 512, it it a great price from Sportsman's guide. It was $368 for members. They were out at the time. I believe they are back in stock. They had the XPS2-0 on sale for $430. That's what I bought. I looked at the 556 and a few others, but they made absolutely no sense to me. I have no intention of using a magnifier. I have iron sights, and I wasn't going to take them off to put a magnifier on. So buttons on the SIDE of the eotech was useless. (No, I don't want a flip to the side mount for a magnifier). Also; who in their right mind "FOR CIVILIAN USE" is going to be using night vision. So basically, I'd pay $150 more for the 556 than for my XPS. About $250 more than the 512. Just made absolutely no sense at all.
Now; if for some reason you really have a need for night vision; and you think you're going to be sniping at 300+ yards and need a magnifier, then the 556 is an excellent sight. Just realize that with ANY EoTech, that if you wear glasses; especially bifocals, or you have an astigmatism, then it takes some getting use to to see the 65moa ring. You have to realize that it's a halogram, not a traditional red-dot. Learn to shoot with both eyes open, and looking at your target "NOT THE SIGHT RING", and the sight ring will overlay fine and be clear. A couple trips to the range and you're use to it. The Aimpoint crowd that says they thing it's blurry, don't understand. And yes; if your eyes are bad enough, you will find it to be blurry at times. But once you understand it, it's awesome. I love my XPS2-0. Then again, I'm not a snob about sights and weapons. I have an A1optic red-dot with a 2x mag built on, and it costs about $75. It's one of my favorite all time sights.