Now, the question is, is it really going to make a difference for you? It may not. I used to swear by my 50 mm/1.4 and now it doesn't like my D2X. Nikon themselves say that the D2X is too advanced for the 50 mm/1.4, go figure! lol! The 1.4 worked great on my D70 though.
If you are a hobbiest, go for the 1.8, and put the rest of your money toward another lens
In theory, the F1.4 is a tiny bit better - it's one more stop for letting in light faster and may be a touch sharper, but not much. The 50mm f/1.8 is one of the best bargains in the entire lineup - it's sharper than basically any other sub-$1300 lens.