GLASS!!
I used metal back at the start of my toking career. they're okay, but they'll get clogged up pretty fast if you smoke with any regularity. Which sucks feeling like you're going to collapse a lung trying to inhale lol.
As long as you don't lose the glass screens they last nearly forever. You still have to clean them out once and a while, but it's ridiculously easy compared to trying to clean the metal (if you even bother) and you'll almost never have an airflow problem with one
I personally just throw the glass screens on the table/in the ashtray after a sesh to knock of the excess ash. Then every once and awhile clean it off with a knife of something to cut out some of the caked on res, lol.
They both do the job, but the more permanent reusable nature of glass is definitely a plus.