50mm or 55-200mm?

[Luna~]

I have a Nikon D300o with a 18-55mm lens.I like to do more macro photography and was looking to get a news lens, either a 50mm Nikon F 1.8 D or a Tamron AF 55- 200mm .Ideally I hope to one day have both of these ,but I'd like to get the advice of people who own either of these.
Also does anyone know of the performance difference between the 18-200mm and the 55-200mm?Is it significant?
Thanks.