Unless you plan to PK or you spend a large amount of your time killing Tormented Demons, you should pick ascensions.
Not only does needle strike set their damage output somewhere around 3% higher than the nox bow when used by an experienced PvM'er, it also gives you the opportunity to use a shield (Even higher dps in certain situations and it opens up the door to Vorago/Kalphite king with t90 weapons).
Ascensions have a higher damage output than any other weapon in the game. They only fall behind mage in PvM situations because of debuff spells, but unless you have 800m to spend on a set of seismics I wouldn't worry about that.