You may not notice it, but automatics consume more power than manuals.  This
extra power consumption comes from heat generated by shearing transmission
fluid in the torque converter.  The fact that heat exchangers are installed
on automatics and not manuals is a testament to the extra heat generation.
For low speed crawling or heavy campers in stop and go traffic, the auto is
probably the ideal choice, but for serious highway miles, I would go with a
manual.  I'm not sure if the VW auto has a lockup torque converter, but if
not, its a bad choice for highway miles.  Then there is the fact that the
manual has at least 4 forward gears while the auto has three.  The gears in
the automatic are spaced out further resulting in extra strain on the motor.
Of course, a lot of the strain is taken care of by the slip in the torque
converter, which results in more heat.....
The auto is apparently pretty efficient, as list people say they can't tell
a difference between the two.  However, the automatic still consumes more
power.  Extra heat is generated by the automatic transmission, and this
requires additional power consumption, assuming the laws of thermodynamics
are valid.