I think template is a very good idea, for learning especially and getting something done quickly ( provided you have enough templates to cover all your needs).
But I prefer building a prefab, then I can maintain and make the code evolve and everything follows. A template is just like "snippets" that you copy and paste. So yes, it's very useful for reference, but in productive environment, a particular template that is pasted in many places will become a serious issue if you have to modify that process even only slightly, you'll have to go and find all the fsm where you pasted that template and modify it manually one by one... ARGH! so prefabs is a much more productive way to keep common tasks, but sometimes is not convenient and practical unfortunatly...
In your particular case, imagine after having pasted all them particle firing templtes on all your various enemies, only to find that you need to fire two different set of particles , or now you go mobile and you need to take in account touches, you are in for a long time to modify everything, if it was a prefab or a more dynamic way of dealing with it ( via of course a more complex system or small framework for that particalar task, be it all in fsm), it would be done, tested and validated already.