That doesn't really address my point. I did agree that the stress argument was valid but it doesn't effect the point of this thread. Given the increasing stress value of each box, it makes more sense to just over channel and to worry less about having to make the roll.
It does address your point.
1. You can't invoke for +2's to your "conviction" for how many shifts of power you can call up.
2. Conviction effects how long your Mental stress bar is and how many extra mild consequences you have.
3. You can invoke for +2's to your discipline roll.
Therefore it is easier to improve your discipline check dynamically, as needed. If you aren't satisfied with a discipline roll and see that an invoke will help avoid backlash, you do it and are done.
Getting to Conviction 5 is important, it means 4 mental stress boxes and the extra mild consequence. Basically it means you can have a 5th (or 6th) spell in a scene (provided the one you turn into a consequence incurs 2 or fewer mental stress).
Belial: They still have to contend with the laws of magic (and other people's perception). The cops might not pay a second's glance at the rod in your hand (3-4 item slot foci are fist/rod sized), but clued in people will view it like a bazooka. In Storm Front, Dresden has a serious "bad ***" reputation, and when he goes to Bianca to try to help investigate the murder of her employee, gets attacked by Bianca because Bianca thinks Dresden did it and is now after her.
But yes, magic is potent.