I am considering selling my 400mm f4 DO and buying the 200-400. I presume the 200-400mm will be considerably heavier.
I will consider the same if the IQ is comparable (or better) to the 400DO.
The Nikon 200-400 weighs 3360g/7.4 lbs so I would think the Canon version would be max 1/2lb more, say 7.75 lb. The 400DO with 1.4X together weigh around 4.75 lbs. So the tradeoff would be an extra 3 lbs.
The Nikon 200-400 is about the same diameter as the 400DO but is 5" longer.
Used 400DO's are going for around $4000 on EBay and the Nikon 200-400 is around $7000 with HST. Tha Canon version?? Probably at least $8000 with taxes.
So an extra 3lbs, 5 inches and $4000 to upgrade.
Will require some contemplation.