If you wear medium armor you can put a lot of points into the medium armor skill line to boost critical rating on your weapon and also on the bow skill line you can boost critical rating. I've found that spells do a lot more damage than a bow so I usually use spells like siphoning (some kind of drain spell to get health back) and also a spell that uses stamina from the shadow skill line. I only really use my bow when I run out of stamina/magicka or I have a weapon that has boosted damage like for undead, daedra, etc. I have a lvl 38 bow skill line I think and I feel like my lvl 8 or so dual wield skill line does more damage. Bow is still better if you want to use hit and run tactics though.