Thanks Bike_On, I'll have to check your link out tomorrow, but I'm always up for a bit of reading.
Just quickly though... This comment below that was copied from another forum gives quite a lot to think about, and could go some way to explain why the mid drive span up more. I think that my understanding of things hasn't really been correct.
"Crank motors are the same as hub-motors in that the slower they turn, the more torque they can make, which means that you can get more help by pedalling slowly."
If I'm correct (probably not) then clearly the torque from the mid drive, was what was making it spin out more. If the hub motor is spinning faster when pulling away, the torque will be lower, meaning that there is less potential for it to spin up. So in effect, this would mean that the mid drive should probably have the edge on the road, where traction is less likely to be lost. If only I could get the chance to test all of this out.
I was back out again this evening on the Haibike, and have to admit that mid drives are pretty satisfying to use.
I think that the issue is, that because they are different, you need to accordingly change your own mind-set, and then suddenly they make a lot of sense.