I'm about to buy a grinder with a crystal catcher but I have a question. I read some where that metal grinders weren't good because there was a possibility that metal shards could possibly fall within your ground up bud? Can some one elaborate this for me? Not a grinder person but thought it'd be cool to have like a little kief catcher so I wanna get one but I'm not sure if I should get the metal or an acrylic one.