The advantages of the knotting vs injection as I see it is that the hair direction should be more like lace in that you should be able to comb it more easily in any direction, since the hairs are not sealed into place.

In addition, it might have less of that stiff "doll hair" look the injection seems to give.

Durability would probably be a bit lower, though I expect still good.

As for the visibility of the knots, in the picture with dark hair I do not see any knots through the base, though this could be different in person. The only thing I see unusual about the knotted skin is you can see it has a slightly irregular surface, likely due to the tiny knots under the skin creating little bumps. I doubt this would be too visible in real life. Still certainly less visible than the exposed grid or knots you might get with lace.

Personally, I'm leaning to trying the injected skin with 1/8'' v-loop hairline, which I have seen some retailers offer.