I’m a 9mm guy I’m finding out. The charcoal filters help A LOT with tongue bite for me and they prevent gurgling. And the draw is just right. The 6mm pipe I have is a bit restricted with the filter in.
I smoke 9mm charcoal filtered pipes on and off. Most of my meerschaum pipes are 9mm. I find it tames wetter tobacco, less bite, I use less pipe cleaners and it wicks moisture. It also changes the character of some tobacco for a different experience. Fun to experiment with.