Just two counterpoints. 🙂
1) On the 60mm. What do you intend to shoot? If bugs be aware your MFD is 7 inches…With a 100mm macro your MFD is 11 inches. That may not sound like alot but it is. My MFD is closer to 19inches and it can b very difficult to get close enough for 1:1 shots without spooking them. Because your DoF is soooo narrow at that, *any* movement whatsoever by the bug kills the shot…So even bugs that dont fly away will still make getting shots tough.
2) Focus speed.
To me, this is a non starter. If your shooting macro you should be manually focusing and when your not your subject is something where focus speed doesnt make much of a difference in determining whether you get the shot or not….ALL macro lenses are *slow* to focus, if focus speed becomes an issue, your using the wrong lens.
this sort of compares various macro lenses without realy getting into somewhat subjective “comparisons”…which is sharper, which hs better IQ etc…..Which for the most part is a non issue with macro lenses…they are all wicked sharp.
http://www.the-digital-picture.com/reviews/Canon-EF-S-60mm-f-2.8-Macro-USM-Lens-Review.aspx