G'day,
Just to add to the replies that have already been given. I must admit I like using braid for blackfishing. A couple of points that you might like to consider though are these.
* Braid has no stretch so make sure you use a good mono leader that has plenty of stretch. Pulled hooks are a bit of a problem when using braid unless you are very careful. Use just enough drag to keep the fish out of trouble areas.
* Make sure you use a long light rod that has a fairly soft tip to help with playing the fish so that not too much pressure is placed on the hook in the fish's mouth. Blackfish are often hooked in the lip which is pretty soft and enables hooks to come out easily.
* My father-in-law, who is a great blackfisherman, won't use this "new fangled stuff". Mono was good enough for him over many decades. He does however grease his line so that it floats and cuts out the belly caused by the line sinking.
Just a few more things to think about. Good luck - give both a try and see what works for you.
Howard