This goes back to old debates and threads of old. At 75, Hagun and Soboro were both solid weapons that you could get the most out of. I'd personally use Soboro ultil your 75 then switch to Hagun. At that point work on one of the Magian GK's, the Epherean ws GK's are the best, followed by the TP Bonus Keitonachi with is fully solo-able.
When I was 75 starting out in abyssea, I found my Soboro started to severly fall behind my Hagun, it might of been a different story with cruor buffs and atma's, but at the time the weapon just didn't work for me. Also note, that Soboro will be best for skill-up's at any level on the way to 90.
Taking a break.