Very interesting, and thanks for posting. No surprise to those who know me, but I much prefer the Martin to the Selmer bass sax. The Martin sounds like a real bass ala Adrian Rollini (my benchmark sound ideal for the bass), where as the Selmer seems to have more in common with a baritone in character. This isn't the only comparison test I've heard involving the Selmer bass, and my reaction was the same in those instances as well.
Of course the parts being played by each in this duet have an impact as well, with the Martin playing the more typically Rollini-ish role with the bass lines.
Still, it's very surprising to me that there is that much perceivable difference between the two tonally.
I own a Conn bass, and although I'd love to have a Martin example as well, I am grateful to have just the one!