I print only black and white. What is the difference, if any to my situation of a 23series Beseler Dual Dichro compared to a Dichro head except the obvious size difference.

1. The dichro head is useful in printing B&W with variable contrast papers.
2. The dichro version uses a diffuser in the light path instead of condensers.

I'm not sure what the difference is but my old color head was a Dual Dichro Color Head and it was a large square unit. I haven't used it in years but I think Dual means dual function because it had lever on the side that was used to swing the dichroic filters out the light path for white light (non-filtered) printing such as for black & white prints on graded paper. The light was diffused

The yellow and magenta filters can be used for printing with variable contrast (VC) papers (same for both heads).