All of this F2.8 vs F4 is mainly dependent on the distance to and subject of your photography. I can get the same DOF at F4 as I can get at F2.8 all I have to do is get closer. But for those who want to get smaller lighter lenses this is a main choice. And with today's clean high ISO cameras it is an excellent choice. For me 16-35mm 24-120mm and 70-200mm would be light holy trinity. All together much lighter than other holy trinity. And there is very good chance that F4 version is sharper than F2.8 version. Canon's is so might be Nikon's.