The +6 Stats enchant effectively only offers +6 Spirit/Intellect for raiding, as stamina is relatively useless there. That is, if you catch aggro from a boss or trash mob, you will be one-shotted regardless of your stamina unless you ice block in time. That said, I don't think the bonus of 6 spirit/intellect compares to the 6mp5 enchant due to the fact that you will only need the extra mana in boss fights as you will be drinking after each pull to refill your mana. That being the case, 6 MP5 gets you more mana than 6 intellect if the boss fight is longer than 75 seconds, which it will be. And, as we know, spirit is essentially useless for a mage in combat without Meditation and/or Divine Spirit from a hybrid Priest. I would definitely take the MP5 enchant, and I hope this helps.
Edited, Apr 14th 2008 2:53pm by IllusiaStratus