When I first started out, I had a couple f/4 and a couple fixed f/1.4. I found myself struggling on commercial shoots. I tried to use my fixed lenses but I was constantly changing between them. The f/4 usually didn't give me shallow enough DOF. So I pretty much sold every thing and went 2.8 with 16-35 II, 24-70, 70-200 2.8 IS.


The 24-70 is the workhorse for what I do. I tried to make the 16-35 "My" lens but I found I was still limited by 2.8 and the 50 1.4 just wasn't fun and didn't have that something, something. So now I have the 35 1.4 and I'm hoping it will have that something, something.


So, I'm of the mind to have the fastest apertures on the most versatile. I usually don't find myself needing IS on short lenses, even when I had the 24-105 I almost always had the IS turned off. 70-200 I find it to be a must have, so I'd say keep the 70-200 f/4 IS if the 2.8 IS is not in the cards.