I agree that the quality differences between the major 6-element lenses is minimal at best. Color rendition however is different for each brand and for that reason I try to use the same make & model lens for all of the formats I shoot. One of the reasons I went with El-Nikkors for this enlarger is that the three sizes I use, 50mm, 75mm, and 135mm all use a 39mm Leica thread for their mount. This allows me to use the Omega three lens turret without any issues or adapters. In addition I know that my filtration will be consistant with each format ( assuming the same film is used in each ).
Best, Harry