People love answering this question, so I'm sure you will have plenty to read. I choose films for their tonality. Different films for different projects. I love experimenting with different films because that's the fun hobby part of black and white photography.
For portraiture, it's APX 100/ Rollei retro and experimenting with Delta 100.
For rock formation projects in bright sunlight and looking for a great tonal look and detail it's APX 25, PanF 50 will replace this film.
Tree pics and meadows are all done in Konica IR 750, this will either be replaced by Rollei IR 400 or Ilford SFX.
When I need some drama on dark wintery days I'll use Tri X or Neopan 400.
All fims are processed in Agfa Rodinal 1+50.
Do I need to use so many different films? Probably not, but they do have a habit of discontinuing my favourite films, so a close replacement is found by reading these forums.