Flavour first and foremost, I find all my fruit juices taste better and cleaner through mesh.
Wicks are easier to deal with, quick dry burn and a blow to get rid of the crud and its good to go again.
Flavour,
And finally
Flavour.
Cons. Can be a bitched to get used to coiling, I Personaly find it easier to mesh than cotton.
Most genesis tanks can't be laid down, nextgen is the exception.
And that's about it really.