Only one year into Canon via my 6D and I realized that I had a serious gap between 70 and 300 so bought the 70-200 2.8 II. This impulse came when I learned of the opportunity to shoot bison as they are being handled at the national park here. In agonizing over this, just like the 300 in February, I read lots on CR and am hoping that the new lens plus my already purchased converters would be useful for BIF since my ability to lock on a with the 300 X2 has been dismal.
As Eldar and others point out a zoom is flexible. I generally don't need that flexibility for the little birdies perched in the tree but sometimes I have a bit of a challenge finding them initially.
Which brings me to another item that maybe should be in a new thread but I'll mention it here. 70 -200 2.8 - almost as heavy as 300, and I immediately missed having my Jobu lens mount "handle". So I put in a day fooling around with a scrap of aluminum and came up with this. Now here's where it gets interesting. I can sight down this "handle" like a gun barrel and be very close to dead on the center of my viewfinder and I'm thinking, hey I can shoot from the hip so to speak without the viewfinder. Is this potentially useful, from you folk who have done a lot of BIF, or a totally dumb idea??
Jack