Okay, the results are in. I went ahead and cut circles from the CC30Y and CC15Y gels that completely covered the bottom of the diffuser and stuck them in. Tried printing the same image with a number of different under-lens contrast filters.
At grade 2, the cold head put out an image roughly 2-3 grades softer than my B22 using grade 2 filtration with condenser head (same negative, paper, developer). The steps between grades with the cold head also seem to be significantly smaller compared to my condenser enlarger. Specifically, going from a grade 2 under-lens filter to a grade 1 produced a barely noticeable effect. Going from grade 2 to grade 2.5 filtration, I was almost completely unable to determine which print was which.
Overall I'd say probably my next set of tests would be to remove the CC15Y filter from the head, since it seems to not need quite so much yellow. However, instead I just got lucky again and picked up a standard condenser head for $75 locally. Much happier with the results from that one, since it basically matches the contrast of my B22 exactly. I'll hold onto the cold light if I ever feel like playing with it again, but for now I'm back to condensers. I'm just waiting on a set of 6x6 contrast filters to arrive from eBay, so I can use above-lens filtration. I didn't actually notice any loss of sharpness using under-lens filters, but all my test prints were only 5x7 prints from 35mm film, so not exactly super demanding enlargements.
Thanks for everyone's help. I think the cold head would have been usable with a little more tinkering, but since I now regularly do work in two separate darkrooms in two separate cities (one with the Beseler and one with my B22 when I print from smaller formats), it's nice to have consistent contrast behaviors regardless of which enlarger I'm using.
