I'd go for a 70-200 f4, because if you ever need low light, you can just stick on the 85, and crop in later, it just seems like the versatility would help in your case.
Unless, you shoot static subjects like portraits, or you need all the zoom you can get, just get the 200mm.
And I don't mean to be rude, but this is a relatively easy question, unless you haven't decided what path you want to take.
They both are equally as sharp when stopped down, so it is all based on your preference.
I stuck with my 75-300, and got a 100mm macro l.
If you still have a 70/75-300 keep it, and get either a 135 f2 or a sigma 150 2.8.
F4 isn't that much of a change, because a 70-300 at 200 is 4.5
That way, you get a telephoto for distance with good light, and when you need low light, you have an fast lens with good enough quality to crop in on.
I've alway been told, you should get the lens that improve your photography, that is why I got some prime rather than a 70-200. And now, since all I need to get better is some more l glass, that is where I go.
So in finale, get the 200 or the 135 f2. And I don't mean to be rude, but getting a 70-200 f4 as your first lens (after having an 18-55 and 70/75-300) is one of the worst moves. All it does is give you sharper images, rather than getting a prime, which makes you think about your image.