I don't think I have ever head of any "main brand" macro lens that is not considered sharp. By main brand I mean any of the major lens manufacturers, Nikon, Canon, Sigma, Tokina, Tamron, Olympus, etc. So they are probably all "much of a muchness" as far as sharpness goes.
Autofocus speed can vary, but for taking photos of static objects, that's not very important.
Longer focal lengths (e.g. 200mm) allow you to stand further away while getting the same magnification as a short focal length lens (e.g. 60mm) would at a closer distance. So a long focal length macro is good if you're trying to photograph a skittish insect, but not so good for photographing something in a small room (as you don't have enough room to move back far enough).
Bear in mind also that if you decide on a Nikon lens, then it will only work with a Nikon camera, and the same for other camera manufacturer specific lenses. A lens from a third party manufacturer like Sigma, Tokina, and Tamron will probably be available in the mount of whatever DSLR you decide to go with.
If you are into extreme macro (above 1:1 magnification), then I would suggest Canon as they have a specialist high magnification macro-only lens. But from your description, it doesn't sound like you are. (And the lens is very expensive as well).