I've been looking into the same exact thing. They had the Omen 35 on sale for Cyber Monday, and with a work discount, I could have grabbed it for $850, but I've held off. I definitely love the look of it a lot more. However I've only recently heard of the Alienware one.. I'm stuck as well.
What I've gathered is VA vs IPS panels. I've also seen reviews of the Omen having much less backlight bleed compared to the Asus and Acer.