so my priest has reached 70 recently and i'm looking to get me some minor healing experience while leveling. i've already healed some instances at 67, which i kinda liked. however, i'm currently wondering about what the advantages and disadvantages are of each spec (disc and holy) during northrend leveling dungeons.

NOTE: i'm not looking for "spec disc" or "spec holy" or "disc is best" or "holy is best" responses (i believe those are also against the rules). what i'm looking for is things like mana efficiency, cooldown comparison, if boths specs use the same skill at different times, things like that. i want to get a decent idea of what each spec is capable of, what the strong points and weak points are,... the stickies are pretty decent at explaining most of it, but i can't lose the impression that, during leveling, some ideas in there are not as applicable.