Crossbows will definately hit harder than Bows, but take longer to reload and not have as far of a range, like in Morrowind. Crossbows were also a bit more cross-hair accurate in Morrowind.
Sorry dude, I have been hunting my entire life. Bows pack more of a punch while crossbows are more accurate. Both can kill you in one shot though. Also, Crossbows take a more considerable amount of time to reload.
That's Bows vs Hunting Crossbows. Not Military Crossbows. Crossbows that were designed/used militarily, were much more powerful than a bow. Like said before, the bolts fired from a military crossbow, were very capable of piercing thick, heavy Plate Mail. In fact, they were designed for it.