Just depends on what and how you shoot. I'm religious about Tri-X 320 when I shoot 6x6. I just like the tones, textures, and the overall look of it. Because of the subject matter I shoot (primarily) I've had to get good at handholding MF down to 1/8th or 1/4th, so shutter speeds are a huge issue. I never use 100 films, but I'll occasionally use Pan F 50 for an entirely different look.