I recently purchased the SIII 8-32. It compares very well with the NF 8-32.
I don't shoot competitively but when I am working up loads it really works well. The glass is really clear and sharp. The clicks seem to be very accurate.
Bottom line IMHO it rates right in up there with the NF. Only problem is it doesn't have a big NF on the side.
I don't have any good Leupold scopes, only and old 3-9 VXII so I can't give you an opinion about how they compare.