"You can't have power and fuel efficiency at the same time. It's one or the other."

I'd agree and disagree. Maybe you can't have them at the same instant, but you can have them in the same automobile. That's the beauty of modern turbocharging. When you demand the power, that smaller, forced-induction engine is drinking fuel like it's a larger engine. When you don't demand the power, like when you are cruising, the turbos aren't spooled up and aren't cramming that extra air, so the engine can run more like a typical naturally aspirated small-displacement engine. I've seen it in comparing my 3.5L V6 Honda with the newer 2.0L Turbo I-4 Honda I had. The forced induction engine had better torque but also got about 15-20% better fuel economy in daily driving. The boosted Ford V6 models vs. the 5.0L in the F150 show similar traits, being more torque down low and better overall MPG when not flogging the engines. On the downside, you do have more moving parts to worry with, and you see less of an MPG gain when you are working the boosted engines hard.

Now with even more aplomb