Depends a _lot_ on the specific camera (and lens). Pro SLR lenses and bodies are generally more effectively sealed than consumer equipment, and generally more robust. A Nikon D5 with a well sealed prime lens will stand up to an awful lot of mistreatment. More, in fact, than the Mamiya he used.
However, medium format cameras are the best you can get for still image quality while still having something you can reasonably call "handheld", which is likely why he chose one. Also, this Mamiya (like most film MF cameras) is massively cheaper than a nikon d5, which means you care less about risk from dust damage etc.
However, medium format cameras are the best you can get for still image quality while still having something you can reasonably call "handheld", which is likely why he chose one. Also, this Mamiya (like most film MF cameras) is massively cheaper than a nikon d5, which means you care less about risk from dust damage etc.