Regardless of whether you go with Kukri or Branched Spear, feats are your biggest problem at low levels. Rogues don't get proficiency with either of those weapons by default, so you'll need to spend a feat on that. When using kukris on a U-Rogue you want two weapon fighting, and the branched spear screams for combat reflexes, so those are extremely high priorities. And I presume you want Roll With It as early as possible. You could take Combat Trick at the 2nd level so everything is online by the 3rd level, which is the way to go in my eyes.
I'd go with the reach option, personally, since the free movement to add distance between you and the enemy that hit you has a nice synergy with reach.