Yeah, Hakka's RBAs are a bit confusing. The bows deal 1d10+11, and the crossbows deal 1d8+10 (the reason is because I took the Weapon Focus feat for bows, but not crossbows).
For granted attacks like Direct Strike, Kriv can choose any weapon Hakka has, since Multiple Arms allow him to change weapons as free action (but only once per turn).
The four weapons have different properties:
· Duelist's Longbow: On a hit, target gets a -2 penalty on ranged and area attacks UENT
· Prime Shot Longbow: Hakka gets +1 dmg with that weapon if he's closest to the target than any other teammate.
· Swiftshot Crossbow: Nothing special about this, I use it because it allows me to make a RBA as a minor action once per encounter.
· Waterbane Crossbow: Extra critical dmg vs water/aquatic creatures (+2d10), and has no penalties when used underwater.
Hope it helps!