Don't own an ACOG but I've had an EOTECH on my AR for 8 years. It's a well built and reliable piece of equipment.
Being a former "pre-optic" Infantryman I was skeptical of anything but iron sights so it took my gun store a good bit of convincing. I just could not get my head around HOW a "floating" reticle could possible be accurate...
I still can't tell you HOW they work...But the do and I would not be without one.