That looks to me like a theatrical hairpiece, rather than one for full-time wear. The hairline is very natural looking because of the graduated random way the frontal hairs are inserted, but to achieve that effect there is a big area of lace with almost no hairs in it. This piece was designed to be seen from a distance, rather than close up. Also, the piece extends down the temples, which is unusual for a man's hairpiece.
To answer your question, if this was intended for full-time wear there would be much less bare lace left at the front, so the lace would not be noticeable. I would say a properly applied lace unit is pretty much undetectable.
Thinskin can also look very good provided it is well applied. Personally I think lace is better for hairlines, but I have heard quite a few wearers say the opposite, so I guess it is a matter of taste. Because it is a mesh, lace doesn't have a defined edge, which makes it hard for the eye to pick up the existence of a base. Thinskin disappears very well against the skin provided it is well glued, but there is always a defined line there (the edge of the base). If it catches the light the wrong way it can show up momentarily, and if the glue fails and the base comes loose it becomes cloudy and visible.
I will PM you a couple of pics of my lace hairline.
Noah