I've been torn between these two as well......and the new 70-300mm IS.
http://www.pbase.com/fstopjojo/image/53825847
http://www.pbase.com/fstopjojo/image/53825846
Seems like barely a quality difference and you gain 300mm and IS for a little less than the L.
Jackal, I have the 70-300 IS, and I rented the 70-200 f/4 to compare the two. In the focal ranges up to 200mm, I couldnt tell the difference between the two. I love the 70-300 IS, for the money I think its as close to a telephoto "L" glass as you can get.


