Is there any difference between combine and union with respect to the difference operation?

Question

In this tutorial union is used to combine the purple triangles which are then cut from the blue triangle below using difference.

IIUC we could also use combine instead of union and it has the same effect as far as the difference operation. As far as boolean operations go, is the effect of using union vs combine always the same?

Answer 1

It depends.

If you have overlapping closed paths, the results will be different for Union versus Combine. If not overlapping, then there's no difference. There can also be differences with the behaviour of Combine itself, depending on the direction of paths.

Examples