Yes the older one cheaper and seriously sharp. It runs in the 460-400$ range. If you don't need the speed of the 50mm lens this can replace it.

The 24-70 is a great lens but if you are using it primary for snakes you will need a real macro. I love my 60mm but the 105 is also very good. I have never shot the G 60mm I can't say how good it is especially shot side by side. The advantage of the 105 is you are back a bit farther the VR is a stupid feature in a macro as VR systems don't work at short distances. I have my VR off 90% of the time as I only use the 105 as a macro. I also have the 105 DF so I use it for everything but macro (far sharper than the macro.)