This varies so much based on build, gear, and damage bonuses.
Plug in your numbers here: http://my.ddo.com/glenalth/85/bows/
Just updated for Bow of Sinew and U9 bane+vorpal specials.
On my AA, vs non-fortified mobs, the Bow of Sinew sits just over one point per hit behind Lit II with bard buffs and around 5 points without. That means it gets pulled out if there is any lightning resistance (since it hits burst, blast, and strike), neutral mobs (lose 7pts from holy), aggro management issues, using a trinket other than bloodstone (spell absorb, feather fall, etc..), or vs weird DRs (hounds).
If I get into that perfect group with a halfling for hero's companion it's my top bow for the duration.
Glenalth Woodwalke ■ Preston the Ranger ■ Brisqoe the Dentist ■ Prescription Liberator
AoK @ Argonnessen