You'll want a wide aperture range, f/2.8-f/32 preferably. Some people are tempted to use the macro/telephoto combos that only stop down to f/3.5 at best, and this may not be enough, if you are going for an artistically shallow depth of field. You also need to make sure the lens you buy has an acceptable magnification factor. The canon 100mm offers a 1:1 mag factor. I'm not sure the 60mm gets that high, so keep that in mind.
One other thing, you need to keep minimum focusing distance in mind. A 70-200 f/2.8 may take incredibly sharp photos and provide some amazing bokeh, its longish minimum focusing distance makes it a poor choice for macro. Example, the canon 100mm has a MFD of 1', while the 50mm's is 1.5'. You want to be able to get closer.