Your 2nd post makes me change my mind
If it was the only scoreboard I was using, definitely the SU. But since you want one that's just for odd times, the Martha one will do you fine. Like Crafter 4 Life, I switched out the Martha scoring tool for a stylus and it's a huge improvement.
Also, if you decide at some point that you want the diagonal board that fits the SU board, it also fits the Martha board - I use them together.