Since all stun damage is physical on the astral plane what would be the advantage to using a manabolt over a stunbolt or vice versa on the astral plane.

I think there is a difference in Stun and Physical damage in Astral plane.

Joker, you may be thinking of spellcasting drain. When a magician is using Astral Projection, all Spellcasting drain does Physical damage.

I believe Toturi's quote from the book only applies to melee inflicted damage.

I've always played that Stunbolt on the astral does stun damage, and Manabolt on the astral always does physical damage.

One does stun damage and one does physical damage. The stunbolt might be a more optimal choice (unless you really want to kill someone), because Drain does physical damage when casting spells on the astral. You want a spell where you can stage the Drain down to nothing.

On the other hand, you can't stunbolt a focus or barrier. You might want some physical damage to be able to deal with those things more easily.

Manabolt is useful if you want to take down a spirit and not have it come back for the summoner. Useful if you're facing a shaman in his domain. With his spirit gone, he'll probably and try and call up another, which could buy you some time.

Stunbolt is basically if you don't want to kill on the astral. OTOH, hate to be the projecting mage who got stunbolted during astral patrol.

Don