I might upset a few people here but these are honest opinions.
I don't think coated braid has a place in barbel fishing. The problem with these braids is the difficulty in getting them to lie flat on the bottom. The only way to do this is to steam them after tying and keep them on a rig board so you are then restricted to a hooklength as long as your board.
I personally think that a good braid is by far the best barbel hooklength in most circumstances, but only in the last few inches above the hook. My preferred hooklength consists of a longish length of mono (reel line or fluoro) of at least 2 ft coupled with a short (4 to 6 inches) length of braid. Join the two with a small rig ring.
The only time I don't use braid is when I'm fishing in a swim where there is a risk of the hook length being abraded - weed, snags, gravel bars, rocks. In these swims I always use a mono hook length. I've not noticed a lot of difference between normal mono and fluoro in these circumstances either in number of fish hooked or in resitance to abrasion.