i'd take underwood, honestly. i think he has more upside.
martin has pretty much proven who he is. and that's a coach that puts an elite defense on the floor, which is good enough to be a solid but not great team most of the time, and occasionally he gets a couple of scorers that pushes them into very good. underwood hasn't proven who he is yet, but there's a decent shot he could have a higher baseline.
i'd also be very happy to have martin, obviously.