@roger,
What I've read tells me, all else being equal, larger wheels generate less rolling resistance than smaller wheels. They used steel wheels, the smaller tested less against another wheel, but against a flat surface the larger came out on top.
I haven't been able to find enough details to know whether axle friction was a factor or not. Momentum may also have an effect.
I would think they took all that onto account, but I see no reason for a larger wheel to have less resistance.