Originally Posted by MaestroAl
One of the big differences is on hills. A human will naturally tend to let their speed creeep up going down hill, getting "free" speed and then let it slowly bleed off going up a hill whereas a computer will back off the throttle going down the hill then bury it going back up, using more fuel.
On flat roads, it's likely the computer will beat the human
Totally agree, and a sensitive foot also helps save the fuel. I've experimented with cruise control on the M74, through the hilly border country, so much easier to get best results with cruise off, while still maintaining the same average speed.