Many pros in my part of the world used Pentax up to the 90s, and Nikons were considered "better" because they were far more expensive so only a few could afford them.
In the 70s my father was a Pentax (Spotmatic) user, while my uncle was a Nikon (F) user.
From my memories and observations:
- Nikon F had changeable viewfinders
- Pentax was lighter
- Lenses were equivalent
- Both could be hauled up a 20,000 ft (6,000 m) mountain and the pictures fomr both were stunning
- Flash sync was similar
- Bayonet mount made for a quicker lens change
- Nikon spent a lot of money giving the cameras away to journalists (call it publicity)
Just adding a few more gasoline to the fire