The smudge brush I use to do a softer liner and more of a smokey effect. I like the bristles are short and compact.
The crease brush again dense bristles, soft not stiff bristles. I use this for apply in the crease, puts the minerals where you want then. You can do a precise line or a more blended line with this brush.
The Sculpt brush, I have only used this one so far to do the crease in my eye, haven't played with it much. The head of this brush is more round compared to the crease brush which is more tapered As with the other brushes has shorter bristles and hold the minerals in the brush and is not a stiff brush.
Now my favorite brush the Angle brush, since everyone knows I am liner challenged among other things. This brush works wonderfully doing a thin line. The bristles are flat and angled and a little stiff but still soft enough not to hurt your eye. I use it wet to line with and the line comes out thin and crisp. I have not used it yet on my brows but I am sure it would work well there also. I think if a MUA is looking for a brush to do precise lines this is the one.
They wash up well keep there shape, I do recommend these brushes if you are looking for some new ones to add to your set.
You can find these brushes and lots of other things at Frends Beauty Supply