Neutrons are much more dangerous, as they will readily be absorbed by atomic nuclei when moving slowly enough, and can form unstable isotopes that might decay by alpha/beta/gamma radiation.
Neutron radiation must be at much lower levels than surface muon bombardment.
Surface muons are used for imaging the Egyptian pyramids, among other things:
https://www.nature.com/articles/d41586-018-05254-2
Neutrons are much more dangerous, as they will readily be absorbed by atomic nuclei when moving slowly enough, and can form unstable isotopes that might decay by alpha/beta/gamma radiation.
Neutron radiation must be at much lower levels than surface muon bombardment.