I’m not terribly well versed in this, but I believe:
The more filled in the better, because you’re making the most use of your space. Which consequently means you get more resolution out of your image size. If your using tiled textures, where you place the seams matter a bit more because they’ll be visible, but for our purposes i believe the best thing to do is aim for the best use of limited real estate in your image. Theres a lot of blank space you could be using in the last image.
