I'd have to disagree with ZorkiKat, or at least disagree that lenses like the Vega-11U are the "best of the best," to quote Woolliscroft's criterion. The Vega-11U is a 5-element design that, in my experience (detailed in my post to the thread to which ZorkiKat links), is very good but doesn't quite match my 6-element EL-Nikkor f/2.8. (Both of these are 50mm designs.) The Vega-11U is a fine lens and I'm not afraid to use it for 8x10 and smaller enlargements, but for absolute nit-picky quality or for really huge enlargements, the EL-Nikkor would do better. As a practical matter, the Vega-11U's long neck means that I can't focus it on my enlarger for enlargements over about 12x16 inches. A caveat about quality: I only have one sample of each of these two lenses. It's conceivable that my Vega-11U is slightly substandard, although certainly there's nothing obviously wrong with it (fungus, etc.).
As others have said, apochromatic (APO) lenses are typically top-of-the-line models and are especially good for color enlargements. AFAIK, my own EL-Nikkor isn't an APO model, and I've never seen a side-by-side comparison, so I don't know how much you gain from that feature. If you want the "best of the best," though, I see no reason to buy anything but a 6-element APO lens. Schneider, Rodenstock, and Nikon are the manufacturers whose lenses most often get mentioned in these discussions, but among these, my own experience is limited to Nikon.