I owned an holosight, and now I own an EOTech.
The only difference I could see is the buttons (the holosight has a non-rubber membrane, where the eotech is nice and rubbery), and the metal hood.
Supposedly, the EOTech circuits are 'ruggedized', but other than the price, I haven't noticed ANY difference in performance. Reticle is identical, and optics are the same.
If you're not worried about dropping it on it's head or looking uber-cool, the Holosight works just fine!