On left the 24-70mm f/4.0 and on right the 16-35mm f/4.0 lens (via CameraSize).
Lensrentals tested the two f/4.0 zooms and the conclusion is:
I will say I’m pleasantly surprised. The Sony FE 24-70mm f/4, while not a great lens is adequate (note I didn’t say adequate for the price, I said adequate) and its copy-to-copy variation isn’t bad. The Sony FE 16-35mm f/4actually is excellent for an ultra-wide zoom, and again, it seems to have decent sample variation. Would I buy them? Probably not the 24-70 f/4 unless I had no options, but I wouldn’t hesitate on the 16-35mm f/4.
I think Sony should remake the 24-70mm f/4.0 lens. Make it more compact and with higher image quality. I know I am aksing a lot but it would make the lens atrtactive again for those who don’t want to carry that big and expensive 24-70mm GM lens!