I see what you are saying. Speed controlled whilst engaged gives you more power than a low level set current control, but I ride most of the time above the cut off speed point for the motor so over a several mile ride it is debateable who has expended the most energy.
In the end it makes no difference. You have energy in the battery that you can convert into motive energy to help you with your ride. If two riders of equal weight on equal bikes apart from one had the controller set to speed control and the other to current control, then they completed the same ride side by side, the total energy expended would be the same. Therefore, the sum of energy from the battery and rider would be the same. If both riders expended the same amount of energy as each other then the battery consumption would also be the same.
The way you're describing your setup is that you prefer to pedal harder on the flat and get more assist up the hills, while as your wife pedals with less effort on the flat and harder up the hills. That's if you don't change the power settings