You should check out this post in the Other Primitive Weapons board:
https://slinging.org/forum/YaBB.pl?num=1603626991. Slyngorm put quite a bit of thought and effort into this very question.
Your list looks pretty good, but there are some arguments that could be made.
Blespi wrote on Oct 19
th, 2021 at 8:18pm:
-cheap and abundant ammunition, you don't have to spend a few days making arrows, don't have to carry around a quiver
I agree that a sling can throw pretty much anything. But the more random in size and shape the projectile is, the more random the flight it will have and the impact it will make after hitting the target. An arrow is a more complex projectile that a glande, but time and effort can definitely be put into getting/making really good sling ammunition.
Blespi wrote on Oct 19
th, 2021 at 8:18pm:
-the stones can be thrown faster, farther, and more accurate than they can be by hand
Mostly agree, but not sure about the accuracy. I think that would be an interesting test. Put a target within hand-throwing range. Throw a number of stones at it by hand, then do the same with a sling. I think I would actually do better by hand. Obviously not with the same power as a sling though.
Blespi wrote on Oct 19
th, 2021 at 8:18pm:
-doesn't require a lot of muscle, can be tired and still sling effectively
Not sure on this. Especially when target slinging for long periods of time, and with larger stones. The body gets tired and throws become sloppy. That's my experience anyway.
Blespi wrote on Oct 19
th, 2021 at 8:18pm:
-trajectory not affected by wind as arrows are
Partially agree. Definitely no where near as much as an arrow. But wind can have an effect depending on the density and shape of the projectiles being thrown. If you're just looking at stones, then yes, any wind effect will be negligible for the most part.
I think your first and last points are the ones I would most agree with. Easy to make, and a small size and weight make it very portable. The other is very similar to your second point. A wide variety of ammunition can be used.