Killing vs. Capturing

[caravel]

The other part of your question was about auto calculations. IMHO yes, the death toll is usually higher and another disadvantage of auto calc. is that it seems to spread casualties throughout your units. - The amount of times I've had to disband trebuchets with a crew of four! This is really annoying, because really your artillery units rarely see the cut and thrust of the melee.

This is because, as Martok pointed out, all of your units, including the archers and trebuchet crews have to fight in melee in an autocalced battle. Missiles don't come into it nor do they confer any advantage. If you play a campaign where you are auticalcing everything your best bet is to train nothing but the strongest sword/cavalry attacking units.