like what rashkae mentioned, they are pretty different. i am not sure if there is a nikon 80-300 f4-5.6, u probably referring either the 70-300 or the 80-400.
for one the 85mm f1.4has a wide aperture that cannot be reproduced when u shoot at 80mm on the equiv end of the zoom that u mentioned. the later having more flexibility at the longer end of things.