Faststone clone/heal function
I use Fastone for viewing only and have never used the clone/heal functions before. After seeing your message I had to try it.
You are almost right, there is very little difference between the two functions. The only thing I noticed is that the heal function seems to apply some sort of blending after you lift your finger of the mouse button. Even so the difference is very slight and is only noticeable when working on textured areas.