Simple: Silica doesn't burn. To clean it - and you can - you actually dry burn with the silica wick in place. You can use the same silica wick for weeks on end by cleaning/dry burning. But you know what happens to cotton with one accidental dry hit...
Everyone has their own likes and dislikes for wick materials, some people swear they can "taste" something about one particular wicking material versus another, and coil build and atty can all effect which wick material you prefer. Pick one and try it - there is no right answer for this.