I prefer the Taming Pole for Fang because I use her as a Saboteur as well, so the increased Magic stat helps a lot (and has only marginally less Strength than the Dragoon Lance).
Even though my main party as been Lighting/Hope/Fang, I think I might upgrade Vanille's Belladonna Wand because she is the best way to beat Adamantoises without a summon. Then I can still upgrade Fang and one other until I get another Trap.