I just bought the RF 20-700mm F/4L. I were considering the f/2.8 version, but I already have a Tamron 70-200 f/2.8 VC G2.
But I have noticed that I mostly use that lens stopped down to f/3.5 or f/4 anyways, so considering that the RF f/4 was much lighter and cost a lot less, it seemed to fit my needs better and I finally went for that version.
It is very light, focuses very fast on both my R6 and R7 and as you can see, the DOF is still very nice
