It depends on the NF model, as the reticles can vary. The mil-R thickness is 0.05 mils thick in the 4-16x42 ATACR, but its 0.036 mils thick in the 5-25 ATACR. Mil-C is 0.04 mils thick in the 4-16x42 ATACR and only extends 5-mils out left & right of center, but for other models it extends out 10-mils left and right.
Personally, I hated the Mil-XT for hunting/cross-over purposes. I prefer the Mil-C in the 4-16x42 ATACR for a cross-over scope. If hunting was the primary factor, I'd get the Mil-R in the 4-16x42 ATACR because it is thicker and will be easier to bracket an animal on low mag. I prefer the 0.2 mil hashes and the floating center dot of the Mil-C, but this is a cross-over scope for my purposes.