Depends, IMHO behavior is easier to use and more logical, because json objects belongs to the instance and is easily accessible that way.
What I mean is the ForEach/Count of the plugin works well for behavior object. They are not needed in behavior itself.
If you have them in behavior, for example you need to pick the correct instance to have a valid foreach (handler,key,value), thats brings all mussy.
They are like system expressions, you also dont have a foreach in every sprite to go through sprites, you have it in system and input the sprite, true?