[orbots]

Memory layout. You can do a hacky "cast" from a homegeneous 4-vector to a ideal 3-vector for free. Same pointer.

[joppy]

This would mean that you have to make sure elsewhere in your code that the last coordinate is always normalised to 1, so do you win overall using this strategy? Plus, the same cast in the other method is ptr+1, which is assumedly just as fast.