If you're planning to cast with backlash, power > control might be a good idea. If your power is 1 greater than your control, you can use your fourth physical and mental stress boxes to cast a spell at your control +4 with an average roll.
That's a bit of a niche case, but it's something.
That's not the worst, I guess. Let's take the scenarios from my first post, and run them from the point of view of "going for maximum effect, willing to take stress but no consequences, and have 4 mental and physical stress boxes, rolling even on the dice".
5 Power, 5 Control - I can go up to a Power 9 attack for 4 mental stress, and then can take 4 physical stress to control the backlash - 14 damage.
3 Power, 7 Control - I can go up to a Power 7 attack for 4 mental stress, I've still got no backlash - 14 damage.
7 Power, 3 Control - Hrm, it actually doesn't work out so well. For a 1 stress hit and a 4 stress hit (for backlash) I can still get up to 14 damage. No better.
The Power over Control person has an advantage in stress taken compared to having them even (which I didn't expect), but still no reason not to favour Control fairly heavily unless I'm missing something.
I do see how for non-attack stuff it is fine to have them be around the same, but again, no advantages to favouring Power.
I'm mostly trying to confirm this is the case and I haven't missed anything subtle, before going off and deciding if I want to tweak it at all.