I use double lightning staves on my MagSorc and hit 50k+ completely solo with only 20 in Spell Erosion. Depending on what your goal is, Lightning Staves are fine. :-)
It depends on your build. Fire and lightning are about the same for solo content. Lightning pulls ahead if you have 75 points in Thaumaturge to gain 10% damage against off-balance, but I think most sorcerer builds are moving away from this DoT-heavy CP setup. In group content it only takes one person with a lightning wall to keep close to the maximum off-balance uptime, and this will usually be a healer or a tank (so that all the DPS can run inferno). Inferno becomes better in optimized groups because fire will deal 10% more damage from the Engulfing Flames debuff. Also burning uptime will be higher in a group with multiple DPS which makes the fire wall hit harder.
Edit: Another consideration is your monster set. If you use Ilambris you'll probably want a fire wall to help proc the fire side. The lightning side of Ilambris will be covered by your liquid lightning. With Slimecraw or Zaan your staff element doesn't matter.