There are 50mm APO Rodagons floating through eBay (multiples per week) and with some patience, you can pick one up for very little money. I have one and also a Schneider APO 45 and I cannot tell the results apart. At large magnifications, they show a bit of advantage over the Nikkor 2.8 and similar Rodagon/Schneider 6 element choices. I only do black and white these days and I think that color workers may see some advantage beyond what I am experiencing. The Rodagon's 2.8 aperture is a bit brighter for composition, etc than the 4.5 of the Schneider but other than that, I'd call it a toss up.

FWIW- I came into a large number of high grade optics as part of a large purchase and had multiple examples of all of the good lenses. I spent some time pondering which to keep and did some testing. One thing I learned beyond these being individual "luck of the draw" advantages is that the APO choices require more care in enlarger alignment. Their sweet spot tends to be more to the open aperture end and depth of field is less apt to cover up any alignment miscues. I played with various systems for this (also fighting with my Beselers to achieve true all-plane alignment) and finally bit the bullet and bought a Versalab which made the process very simple and intuitive.