Size, shape, material

I don't have a meer but briar vs cob there's a difference. There's an even bigger difference between briar and gourd. Seems the cob tends to mute citrus notes and the gourd does the same but even more so. (I don't smoke Va flake in my gourd - it seems kind of pointless.) The gourd mellows very strong (and potentially harsh) blends making them a joy to smoke. Straight vs bent, not so much but bents seem like they gurgle quicker than straights and I hate that. Also, the deeply bents sometimes won't pass a pipe cleaner meaning you're screwed if the draught hole plugs. 'Dry system' type pipes almost never pass a pipe cleaner so I avoid those like the plague and won't usually buy any pipe with any more than a mild bend. Gourd calabash pipes get a pass on the whole pipe cleaner critique because even tho they won't pass a cleaner, the smoking qualities more than make up for it. Not only that but you can always pop the bowl out and poke at the hole with a pipe cleaner or a match stick if it plugs, although that's probably against the rules somehow...