I rode two different ebikes. Both are 250w with similar sizes batteries. One had a mid drive and the other has a rear hub drive.

The mid drive seems to have significantly more in terms of efficiency.

It also has what imo is a less efficient gear system. The hub drive bike has a Shimano GRx derailleur system while the mid drive bike has a belt drive and a nuvinci hub.

I think the reason for this is that a hub motor inherently is less efficient than a mid drive because it has less favorable conditions. Hub motors typically have 5:1 gear ratios. Mid drives have 18:1. So the mid drive can more easily be in the optimal power band while a hub drive motor spends more time and power in non-optimal situations like starting from a complete stop.