Well, even my +5 VVS Haedonggum (120 ATK) is better than a +4 Fireblend (100 ATK) even though it's a Lvl 4 weapon.
Soo... +7 VVS Fire Flamberge (150 ATK) will be much better than the Fireblend as well.
ATK wise,
Fire Flamberge > Fireblend.
If you don't have INT, the Fireblend's Fire Bolt is pretty much useless anyway.
If you have INT (-> Paladin, Crusader), I doubt you'll melee much with it - to get the additional Fire Bolt damage.

Uh.. SinX is a possibility as well. You wanna use it on which job?