Now that Tom's has done a decent comparison between the 480M and the Mobility 5780, we need to see how the 480M stacks up against 2x 5780's. These are the two top of the line offerings from Origin and there is about $300 between them (the 480M being more expensive). I don't need Tom's to do this if anyone is aware of this comparison being done anywhere else (though I know Tom will do it right).
It also depends on the situation (can it take advantage of the Xfired GPUs, etc.
In general it will be 2>1 , however for some applications that may not be the case, just like for some situations the MR HD5870 will outperform the GTX480M, just need to be aware of if it applies to your needs.