The 2826/10 engine has lower MR resistance than the 2820/12, so probably greater current consumption.
Nope. Exactly the opposite, in fact. The system as a whole converts electrical energy to mechanical energy. So for identical mechanical power outputs, the electrical power input must be the mechanical power output plus all the losses in the system. All else being the same, a higher winding resistance means a higher electrical loss in the motor (which is part of why smaller motors get hotter), which means more current needs to come from the batteries.
As noted in earlier posts, people's actual experience shows that the difference isn't much, which shows that the optimal motor vs. efficiency tradeoff is pretty broad. This makes all of our lives easier, because we don't have to obsess on getting just exactly the right motor. (Well, it makes
your lives easier -- I'm still flying slime).