Those AWFUL 70-200 Nikon Zooms! ;-)

Another way of looking at it is the Mk II does not breathe - in the it sends it holds  angle of view as you focus closer.

This is a very desirable feature for video work.

I presume because the Canon f2.8 does not hold angle of view the same way the OP acknowledge in this respect Canon make themselves second in video

As I shoot video I prefer the Nikon f2.8 option.

I do not know a lot about the Canon f4 version but doubt it has the optical quality of the Nikon, five stops image stabilisation or automatic tripod mode detection. These might not be the features the OP wants, but they look quite interesting to me as a potential upgrade route combined with a 1.4 X converter for flower and insect photography from the 70-180 macro - another lens Canon never made  

--
Leonard Shepherd
Many problems turn out to be a lack of intimate knowledge of complex modern camera equipment.