You have two very close choices. Refurbished isn't a bad thing but it is an unknown thing. They can't sell it if it doesn't work. The cause of having the laptop sent back and repaired could have been as trivial as a scratch on the screen, or bad RAM. One thing I am wondering is if that refurbished is all covered in warranty, I am assuming so. That choice is just then your peace of mind. (Just knowing there WAS something wrong and they "FIXED" it)
As for the competitors, I think Alienware has premiums for their products and that you are buying a name. A friend has had a hell of a time dealing with them when he bought his laptop and their customer service was lacking.
I have only read good things about Clevo's. I own one and it is powerful but it has some quirks that must have only been present in my computer. That gfx card will handle anything out there right now, you don't NEED SLI.
As last words, both will perform well. If the Alienware is warrantied and you are fine with that peace of mind "refurbished" that is a good deal. But I personally sway to the clevo