I have used DiXactol quite a bit. It works well on larger formats with fine grain films. In 2 bath it is about N-2 and with Tri-X it is very grainy even in 6x6. It seems a little finer grain than PMK and has very good accutance and highlight separation. - Split D23 also seems to do this with finer grain though. I think I'll stick with PMK and TRI-X for 4x5 and am still experimenting for 6x6. I find that film speed is important and FP4 in Dixactol needs to be about ISO 64.
Frank