Witch one is sharper? I need to rent one of these macro lenses for some archival work with a measly T1i body. I can get most of the detail i need with a 50 1.4 but not quite enough. Is one of these lenses much sharper than the other? Will the 100mm really bring me in further than the 60? The 60 says it can focus a minute amount closer (60mm Closest Focusing Distance 0.2m /0.65 ft. vs. 100mm Closest Focusing Distance 0.31m / 1 ft. (film plane to subject) Im planning on using a tripod and i might be shooting tethered.
Im also planning in getting a macro ring light MR-14EX to go with it.
Those are my only two option for lenses aside from a MP-E 65 f/2.8 1-5x Macro but im not really sure how to use that lens.
Archival work of what? Documents, paintings, drawings, statues? It sounds like you want to be close.
You should look for a lens that is equally sharp at the center and borders with low distortion. Most Macro's are pretty good, but since you are on a tripod and tethered, I'd go for a Zeiss 100mm Macro. Manual focus is a breeze when tethered to your computer.
Its better by far for your work than the others you mentioned.