Cotton pro:
Many people claim cotton tastes better.
Many people are worried about silica wicks shedding fibers that will lodge in your lungs and possibly cause or contribute to silicosis. Cotton is biodegradable and shouldn't cause any lasting issues.
Cotton is cheap and universally available as both cotton balls and yarn.
Cotton con:
Cotton burns easily. One dry hit (or mostly dry hit) and the wick is toast. Silica is much more durable, and it allows for dry-burning.
Some people don't like the taste of a cotton wick.
Good post. All I can say about that boogiebear about silica is, after 39 yrs of willingly sucking down cancer, a bit of silica really doesn't frighten me. When I'm gardening, and pouring sand, I probably get a lot more silica in my lungs than from an atty's wick.
But those dry hits on cotton... UGHHHHHH! Like setting your jeans on fire and huffing it... ughhhhh And as you said, all you have to do is scorch it a LITTLE, and that's it, it just tastes awful after that, and you have to get up and go change it. Silica doesn't do that, and it doesn't give dry hits, either.
Andria