I've used both. Like both. Really kind of depends on which one works better for your eye. I'm planning on getting an EO Tech myself.
I borrowed one at a recent 3 gun, mounted on the handguard of an M4 carbine. With the EO Tech and an unfamiliar weapon I was able to get 6 hits on a target at 40 yards in 1.8 seconds from the low ready. With practice on the sight I bet I could shave more time off of it. With that huge outer circle, you can just center a target in it and blaze away. I used it again at a 12 inch plate at 180 yards and hits were super easy.
I've also used the Aimpoint in competition, borrowed a Bushmaster with one mounted when my rifle broke half way through the match. Hits at 200 yards were a snap. Very fast sight.
Between the two I find that the EO Tech suits my eye a little better, and I'm planning on getting one when I can afford it.
I know that the EO Tech has less battery life, which may be an issue an issue. But I believe both are extreamly durable, as both seem to be extreamly popular with the troops.