Thoromin,
Leather vs. mail has always been a hot topic of discussion.
Bottom line is, whichever gives you a better upgrade.
In raids, the armor rating doesn't matter since you will get 1/2 shotted anyways.
If you look at Agi and AP, you might find that leather armor give more of these then mail does,
However, do know that in raiding intellect is essential to hunters as we are one of the fastest
classes going oom.
If you're leveling, then some leather gear is fine as mana isn't really an issue,
at 70, if you have a leather epic vs a mail green, then def leather is better. Just
check out the stats, but do remember that intellect plays a part in it.
-Og