I'd go with 200-400 for the following reasons
- zoom range of 200-400 and 280-560
- convenience of a built-in extender
- price is reported to be lower than a 400
- if you want one super tele this would be it
I'd go with the 400 for the following reasons
- f/2.8 for when I need more light or more background/subject seperation
- weight as it is reported to be lighter than the 200-400
- physical length is more often a problem in shipping than physical width
- if you have more than one white prime this would be it
Dimension comparison between the 400, 200-400, 500, 600 and 800.
Reported to be heavier than the 400 (3850g). So does this mean the 200-400 is lighter than the 600 (3920g)?
MFD is below