Optically the newer AFS lens improves on the older lens in most areas. But the older lens is pretty good too. The only complaints on the newer lens is auto focus speed. Yes it is a little slower than the older lens but maybe not enough to affect your shooting, unless you use it from one end of the court to the other. I think it's slower speed is due to the long 180˚ focus throw versus the older lens 140˚. I was looking for an 50mm f1.4 lens about a year ago. My son bought the new AFS 1.4 version and I compared it to my AFS 1.8 lens. The new 1.4 lens was slower focusing and I wasn't comfortable with it. That's probably just me. I ended up getting a used AF 50mm f1.4D and am quite happy with it. I say try them both in a local shop and you decide.