The xbow does not deal 2 times the damage a bow does, because of base damage, on orcs I crit for like 950 with bow, with xbow I do like 1050. Not too much difference. It is all a matter of personal preference, neither is better then the other.
diff build will go diff weapon
if ur a spr + str, go bow
spr + dex, go xbow
full str go bow
full spr i have no idea
full dex xbow
full int plz kill ur archer now