Letting the AI choose your path for long-distance moves seems like begging for a close encounter with a minefield or an enemy unit. Given half a chance, the AI will generally get you blown up or shot to pieces, in my experience.
I use short bounds to avoid the known minefields and irate enemies the AI seems to delight in charging into. Once I'm clear of those I'll turn on the reachable hexes, but I still won't use the full range, at least not initially, because I want to be able to back off if I bump into unspotted bad guys. At any rate, I don't see speed as an issue. By the time I can take a swallow of the cold beverage du jour, the Artifical Idiot generally has finished calculating a disastrous route for the fastest of WWII units (I don't play the moderns, though, so don't know about that.) I'd much rather see the AI given the ability to avoid known minefields and enemy zones of control than have scarce programming resources spent on producing unsatisfactory results more quickly. :rolleyes: