I have the 50mm F2. The other lens is the 35mm F3.5
By all accounts, these are both excellent lenses and neither will dissappoint you. There is a test of the 35mm macro in the August Shutterbug.
The less expensive 35mm has the advantage of actually getting 1:1 image where the 50mm isn't quite as close (stated as 1:2 but measured in several tests as closer to 1:1.6).
The 50mm is a faster lens which I find helpful with tabletop photography where I don't use a flash andI depend on diffuse lighting. The 50mm is also one of the weather-sealed top-of-the line lenses.
Check ot the "Close up" section of the "Post your photos" board here and see my "Caterpilar eating my Parsley" picture done with the 50mm. And check out the same are for my "Little Mutant" photo posted about two months ago (kinda' buried so try this link)