There is reason the F4 costs less. I have one of the 50mm f2.8 and love it.
There is that much of price difference between the two and since any print
you goes through the enlarger lens its not the place to scrimp. As with all
things the chain is only as strong as its weakest link. The final print is
what matters, but it can to achieve with lesser equipment. Most six element
enlarging lenses are far better than 4 element lenses. The main difference
is usually is contrast in fine, especially at the edges. The El- Nikkor 50mm
2.8f is bargain at its price.

Sheldon Strauss
www.shel.focalfix.com