Chainlighting vs. Lightning

[jedimaster86]

In my experiences with a lite sorc (never used her much for MF, she was a keyer/rusher/etc; blizzard was my MF), I have found regular lightning to be much more useful. It won't suck your mana pool dry as quickly, I think it generally does better damage (not that you'll ever know when your attack is doing many K's of damage...or 10 damage), and you can simply tele strategically to be able to zap your arcs right through all enemies. If you are doing a lower-level area, CL will better, but if you're on a tougher stage, I'd use lightning.

If you are only lightning (I'm assuming not, since you're asking about only investing in one), you'd just want to max both for the synergies anyways, and like Blue said, see what works best for you.