As others mentionned, I'm not really favorable for "stats" if those would grade your power output compared to others.
 Unless you intend to make us fight each other later on in the RP, I don't feel like giving stats to powers is much needed. Also, turning powers into statistics removes a part of what RPing is and turns more into a "game".

But with the example you gave, if it's to scale how efficient your character masters some aspects of their magic. I'm not totally against it. However, I much prefer to go into the abstract side of things.