I'm probably not the best guy to answer since I have not only the 3.5 and the 2.8 but also the uncommon f4 version. The reason is that each has overlapping strengths, so some areas 2 lenses are better in one area. The 3.5 has less flare and ghosting of all, 4 is close 2nd and the 2.8 is side by side less good. Sharpness is around the same, the 4 is very sharp and equal of the 2.8 at 5.6, the 3.5 seems less sharp for distance/landscape but really good closer in, which the 2.8 gets very close to matching. If you really need the speed and can deal with the added flare get the 2.8. If you need better distance get the 4 or 2.8, if you need better closer in get the 3.5 or 2.8. Sorry, thats the puzzle, no one 20 does it all exceptionally, which is why I have 3 of them! I do find that I've been using the F4 model quite a bit lately on my D3.