difference between artillary line and missile line?

as the title says.

i dunno maybe if you play against a comp he will attack your artilery units than the missile units?

Artillery can miss, missiles do not. Basically even if it it looked like a missile missed, it will still hit the target for full damage. Artillery always does damage where it looks like it hit.
(I'm pretty sure thats right)

Thanks Grater. Always wondered about that.