He's asking for a choice between two valid professions, Alchemy and LW. No need to be a jerk about it.
Tribal LW will get you the Windhawk set, good for healing and caster DPS. You can also use drums for various temporary buffs. Alchemy gets you a couple nice trinkets and the ability to use Mad Alchemist potions, a cheap and effective substitue for mana pots.
I think for casters, I would take Alchemy over LW. If you're chain-chugging mana pots, the extra 40% when you have an alchemist's stone equipped makes it worth the profession slot. I have also heard good things about DPS groups setting up a rotation for the haste effect from drums of battle, so YMMV.