Al:

What I've noticed is that the AI Crusades seem to have much more freedom than I do to weave through provinces. I'm always limited to a couple of options, usually fairly much straight enroute to my crusade goal.

The AI seems to go after the most lucrative sources of recruits, meaning high Zeal and high numbers.

As has been posted several times, send one or two Inquisitiors ahead of your crusade to increase Zeal; I think it helps get more men.

ichi