This is the best comparison between the two (and other machines beside):
http://www.anandtech.com/mac/showdoc.aspx?i=2816&p=1
The threads here aren't particularly illuminating - the key point they make is the value for money. Buying new, the cost and difference in processor speed between them means that the 2.66 gives you
far more bang for your buck. As a option, the 2.0 hasn't been a popular one and this is the main reason why there aren't many benchmarks around. You could try Macintouch for reader reports, though.
The refurbished price makes the 2.0 model makes a much more viable proposition in my opinion. Of course, you can always upgrade the processor - anandtech.com has a guide to this, I think.
The 2.66 machine offers far better value for money as I say, but if the most CPU intensive stuff you'll be doing is home video, the 2.0 one would fine for you.
Of course, the cheapest option would be going for something like an iMac, but I'm sure you've thought of that!