Which is the more powerful video card?

I have an Alienware m17x with dual ATI 5870's Crossfire. Alienware is sending me a brand new Alienware m18x with Dual NVIDIA GTX 460M's SLI configuration for my troubles. I looked online and it would appear that the SLI configuration is actually slower in benchmark than my current configuration. Does this give me leverage to call them and say that I want the AMD 6970 crossfire configuration instead? Or is the SLI configuration faster?