I mostly use capsules. It keeps things clean and also, when traveling, it’s really nice to preload caps and have them ready, rather than fumbling around grinding, filling and cleaning.
That being said, I leave the cooling unit screen in. It always gets dirty with little herb bits that come up through the top of the capsule. So, in my case, if I didn’t have the c/u screen in, these bits would go into the cooling unit and possibly, into my mouth. The amount is not insignificant. Maybe I’m drawing too damn hard on the mouthpiece? LOL.