I stock and use several developers. The reason is that, even though the results may be subtle, there are distinguishable differences in print developers. These differences amount to print color and tonal separation. With the exception of Zone VI print developer all of the other print developers that I use are formulated from componant chemistry.
Insofar as film developers I use pyro developers as a "class". At this time I primarily use Pyrocat for the low general stain to high proportional stain ratio. The reason that I use pyro developers is that the proportional stain increases better highlight separation and also serves to build higher density range (contrast) in the negative for printing on Azo then non staining developers. As with the print developers, I also formulate Pyrocat from individual componant chemicals.
Hope that this helps. Good luck.