>>more rolling
Are you sure? I'm sure there's some sort of curve, but road bikes are generally more efficient with larger wheels up to a point (29 is much more efficient than a 2) and, again, mountain bikes have upsized as well because if you hit any sort of irregularity, with a large wheel it's not as steep of a "climb"
But with a big wheel, you have to set it motion, which is costly, which is why I was thinking big wheels would be bad for stop and go and good for cruising at a steady speed.
>>27.5
I went straight for a "niner." It felt very cumbersome to maneuver at first, but the advantage in terms of rolling resistance and traction (contact area) were worth it for the non-technical stuff I ride.