Got a new chest the other day. A sidegrade. So I was trying to decide if it was worth the cost of gemming and enchanting it. Gems are easy due to my professions, but 10 Stats to chest is still somewhat expensive.
Anyhow, it got me thinking about going with a different chest enchant and I came to the conclusion that 10 Stats isn't even the best one to use anymore since I haven't Plea'ed on CD in a long long time. Assuming even a relatively high Plea usage of three times in a six minute fight, 10 MP5 gives more mana back than 10 Stats or 250 mana.
In a six minute fight, you get:
10 MP5 = 10 MP5 [720 mana]
250 Mana = ~8.58 MP5 [618 mana] (250 starting mana plus 188 regened by 3 Pleas plus 180 regened by replenishment)
10 Stats = ~6.22 MP5 [448 mana] (182 starting mana plus 136 regened by 3 Pleas plus 130 regened by replenishment)
This, of course, puts no weight on the Stam, SP and Crit gained from 10 Stats. Weigh that as you will, but I've switched to 10 MP5.
Edit:
Uniformity in numbers, total mana gained and clarification on fight duration.