[JimD]

The lockup of the torque converter in modern automatics is a good point I probably should have mentioned. That makes it equivalent in transfer of power to the manual but only when the lock is engaged. It is not engaged while shifting and typically not at low speeds either. The best it can get to is equal, it can never be better in transferring power.

Lots of gears is a bit different point. Every engine has a rpm range that it operates most efficiently. It will not be high in the rpm range due to frictional and windage losses. Having a lot of gears allows the engine to be in that optimum rpm range more of the time. But there is not reason that automatics should have more gears than manuals unless you make the assumption that manual transmission drivers won't shift 8 times to get to top gear. I think Chrysler put a 9 speed into the Cherokee and the reviews indicate the vehicle almost never gets to 9. I drove one as a rental and couldn't tell exactly but it did hunt around at highway speeds trying to find the lowest ration the engine can pull. That sort of messing around would possibly get annoying with a manual.

But my main point stands. Mechanical efficiency of energy transfer goes to the manual. That can be more than offset by unequal gear ratios but there is no need for that to be the case.