I got the following answer via Twitter (https://twitter.com/#!/bortzmeyer/status/132090094067785728 https://twitter.com/#!/bortzmeyer/status/132090094067785728)

I got the following answer via Twitter (https://twitter.com/#!/bortzmeyer/status/132090094067785728 https://twitter.com/#!/bortzmeyer/status/132090094067785728) "@adulau Knot is faster, according to the benchmarks made by its authors. But NSD is production-ready and Knot is alpha (or less than that)."