ALDOR or SCRYERFollow

I am a 70 frost mage with mining and engineering; which should i choose?

I am a 70 Holy soon to be protection Paladin herbalist and Blacksmithing; which should i choose?

19. "Aldor or Scryer?"
You're the one that has to make that decision, but you can make it an informed decision by looking at the article in WoW-Wiki that compares the rewards for each faction.

http://www.wowwiki.com/Comparison_of_Aldor_and_Scryer_rewards

Also from WoW-Wiki, the following advise, if you make a wrong choice (thanks to Agobi for the heads-up on this):

Switching to Scryers

To change your faction from Aldor to Scryers to access their crafting recipes (and undo all reputation progress you have made), find Arcanist Adyria, a Scryer in Lower City. She offers you a repeatable quest [62] Voren'thal's Visions, that requires you to find eight Dampscale Basilisk Eyes. Once you are Neutral with the Scryers you can no longer receive this quest. The quest gives you +250 Scryer rep and -275 Aldor rep (in bonus, the quest also gives you +125 rep with The Sha'tar).

Switching to Aldor

To change your faction from Scryers to Aldor to access their crafting recipes (and undo all reputation progress you have made), find Sha'nir, an Aldor in Lower City. She offers a quest that, upon completion, allows a repeatable turn-in quest. The quest require eight Dreadfang Venom Sacs. Once you are neutral with the Aldors, you may no longer receive this quest.

i didnt see any engineering rewards for either.