I like Tri-X/PMK for medium format, but if you want something finer grained with nice shadow detail and delicate highlights, try Delta 400 Pro at EI 200 in Perceptol.

If the new Delta 400 were available in sheet sizes, I'd very seriously consider using it instead of Tri-X. I use Tri-X in medium format in part because I like having some consistency of tonality across formats.