No idea between the 60mm. I found that working distance seems to be short on the 105mm, so I would guess that the 60mm is even less.
If you want a decent macro lens and aren't in a hurry, I'd try as many as you can, either through hiring or borrowing (in a camera meet perhaps).
105 and 105+extension tubes are crisp (you can see examples in the siggy link)
Tamron do a 90mm that is meant to be very nice too.
Sigma do a 105, 150 and a 180. Depending on arm size and working distance. I've read on here that the 150mm is pretty decent and with a working distance that doesn't scare the subjects off (dragonflies are very skittish!).
Personally, see whether you could get your hands on the different ones, then see whether there is a used version for less...
Good hunting!