I prefer Marshal (one l, Freeling's usage notwithstanding) in part because
there are a lot of piece-names that start with C and I often strive for
unambiguous English notation. I also tend to use Archbishop instead of
Cardinal for the same reason.
I'm not sure there is a consensus for Chancellor or Marshal, but I would
use neither name for any other piece-move. Both names seem to be strongly
associated with the specific R+N combination.