Is it better to have one audio source on the player or one on each collectable object?
The sound effect is to be played for each collectable upon collection.
I am targeting iOS so performance is important.
Definitely on the player. The only reason to put it on another object is for the 3D/volume falloff effects (and the management of loaded sounds if things are created/destroyed dynamically). If it’s being played when the player hits it then there’s no reason to put it on the collectable.