I shoot with a m4/3 system so my macro lens is a 60mm which is equivalent to 90mm on a DX system. It's a great lens for really small stuff and has the reach to keep back a little from skittish critters.
The right diopter was a challenging choice. I found it very hard to choose as there are not many comparisons on line. In the end i was able to borrow the Subsee +5 and +10 and test them on my camera, you can see the results at the link. i use the +5 most of the time, as it gives a little more working distance and makes lighting easier. But this is specific to my lens/camera, so advice from someone with your combo would be a lot more useful!