New Rogue Seeking Advice

[P99SToRM]

Hello everybody, i recently started a rogue in this server, and i finally received my Backstab skill, now i've gotten so far only 2 weapons.

Fine Steel Dagger: Dmg 4 / Delay 19
Great Snake Fang: Dmg 5 / Delay 27

FSD seems to have higher ratio while the GSF seems to have better max damage... Which one i should be using right now? And when i receive DW at lvl 13, how should i decide which weapon to keep on my primary slot.

Sorry i been reading a few of the damage calculation guides on the forums and wiki but i am confused.