Faster Attacks or Added Fire for GS/HS Build?

Right now I am running just 4L on both as I am waiting for items to sell before I upgrade. The way the links look like:

GS -> Melee Phys -> Multistrike -> ?
HS -> Melee Phys -> Multistrike -> ?

So I am wondering which of the two would be better for the fourth slot.

Added fire shows higher sheet dps but it is a higher level and has 8%Q over faster attacks, so that's not really reliable.

^

FA. The only exception is if you're mana based and FA causes you to go out of mana too soon/too often.

For GS, also consider Conc Effect, especially if you took Amplify.