Originally posted by IgorZ that's interesting... I guess you are one of the few people who had a chance to try both. Why do you prefer the F if you don't mind me asking?
Sorry, I can't give you a good, definitive answer
The only real difference should be with the coatings, several of the F and FA lenses are the same optical design, but when I've come to decide on which lenses to sell or keep I've found that I have sold my FA 50/1.7, 50/1.4, 50/2.8, 100/2.8 135/2.8 and 300/4.5 and kept all the F series equivalents. I don't know if there were any changes to AF mechanisms between the 2 series, but several of the F series do seem to have a fast, almost violent, autofocus which can also be quite noisy.
I believe that the FA series is able to transmit more data to the digital camera bodies (MTF?) - but I don't know enough about the benefits of this to say whether it is significant in making a choice.
I think you would be equally happy with either version, although in my experience the FA's tend to come up for sale a bit more often