I’ve prepared a rough comparison of all the professions available ingame and provided a brief analysis from a discipline priest perspective.

The document via google docs.

In terms of optimal spellpower amount Jewelcrafting+Tailoring would be the best mix. However, Enchanting+Tailoring is pretty viable as well. First of all, you get to enchant pieces of armor that normally aren’t to be upgraded – mainly rings. Second, it’s easy to

Now, the Jewelcrafting bonus is pretty straightforward. We’re simple people, we see spellpower, we take it.

Let’s take a look at the Tailoring perk. Darkglow Embroidery supplies 400mana every minute while Lightweave Embroidery provides you with a 295spellpower proc for 15 seconds. Both have an inner cooldown of 45 seconds.

Now for obvious reasons, I wouldn’t recommend getting the Darkglow Embroidery unless you have mana issues. Other than that, Lightweave all the way.