The length of the patch has more of an effect, since you have to rotate that wheel over the flat length of the patch. Since the wider patch may result in less width it would be more efficient. Trains are efficient because steel wheel do not deflect much so there is no flat part of the patch to overcome. Another argument goes that the comfort being greater on the wider wheel allows the rider to be less fatigued over longer distances.
Arguments to the contrary are that narrow tires can generally take higher pressure which also decreases the length of the flat part of the patch. Narrow wheels are also lighter, but then so are smaller wheels. There less loss to side casing of flex.
In the past I have put Big Apples on a couple of bikes where there was enough clearance for them. The comfort level improved with no noticeable change in speed.
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