I've used a 50mm f/4.0 El-Nikkor since 1972 (not a typo!), and it is a
superb lens. I use a grain magnifier for focussing the negative, so
maximum aperture is not an issue -- I definitely recommend getting such a
magnifier.
The only time I longed for a faster lens was when I tried the original
Cibachrome material in the late '70s. I seem to recall exposures getting
close to one minute at f/4. I don't know whether that's a problem with
color materials these days or not; I don't play with that stuff these days.
If you're doing mainly B&W, I'd say spend the extra money on film & paper!
Regards,
Steve Alred