cjc2 wrote:
I have both and I use both regularly. The 2.8 is the better of the two by far, IMHO, yet when I don't need its speed I do use the F4 because it is substantially lighter. The F2.8 version is sharper and faster focusing and has more features than the F4 version. Best of luck.
I opted for the f4 due to weight more than cost.