In their epic review of these 120Hz displays, Tom's gives Acer points for excellent contrast while praising the Alienware for superior color. Both seem equal in terms of actual 3D (and much improved from the previous generation of 3D LCDs), which makes sense given that two monitors with equal refresh rates and resolution are being driven by identical graphics cards and looked at with identical NVIDIA shutter glasses.
For Tom's, it comes down to amenities, which they feel Alienware nails with extra ports, a nicer build and a swiveling display. I personally just dig that orange finish. Since the OptX AW2310 is on sale for $450 at the time of this post, it certainly sounds worth the $50 premium, should you want to enter that whole 3D glasses lifestyle. [Tom's Guide]