Choir Miking - KSM137 or SM81

Date Updated: February 22, 2018 FAQ #2665
I am trying to choose between the SM81 and KSM137 to mic a choir outdoors using sound reinforcement.1) Which one would be the best to use?2) What are the primary differences?3) Which one would you use?

1) The KSM137 is quieter (less background hiss).
2) The self-noise level and the SPL clipping point.
3) The KSM137 with the A81WS windscreen, and the A53M isolation mount.