Priests will constantly argue the validity of their spec but when it's us against paladins, shamans and druids (sorry guys we still love you) for a seat in 5/10 mans we have to remember one key thing: Invite the player not the class. That being said the choice between Disc vs Holy really does come down to play style. This post is not to argue which one is better but to provide info.
As of 4.0 Our mana pools are smaller...oh for the love of god smaller
Choosing the right spell at the right time is important
Spam healing is really no longer and option
Disc is still excellent at single heal (Penance/DAg/PWS)
Holy is still excellent at group heal (Po/CoH/LW)
What to stack?Holy Intellect
Spirit
Stamina*
Haste - If you can't heal fast enough (to 12.5% raid buffed)
Mastery - If you use your Mastery spells a lot
Crit - If using many of your spells regularly
Disc Intellect
Spirit
Stamina*
Haste - If you can't heal fast enough (to 12.5% raid buffed)
Mastery - If you use your Mastery spells a lot
Crit - If using many of your spells regularly
Logically, if you can't get the heal on the target fast enough, a crit on a corpse is kinda useless. So in general Haste then Mastery or Crit.
Hit isn't really in here. It's more for DPS, besides we have much more important things to stack other than hit.
Note on haste: It's pretty shiny and ooooo fast heals...but be careful you don't stack haste to the point you burn out your mana pool when we get click happy.
Note on Stamina: It's only included in the list cause it's there anyways (besides life = good, just
don't go reforging to add stamina to rival a tank)
Disc
http://elitistjerks.com/f77/t110244-cataclysm_discipline_priest_compendium/
http://wow.joystiq.com/2010/12/20/spiritual-guidance-discipline-priest-101/
http://www.tankspot.com/showthread.php?72694-Discipline-Priest-PvE-Guide
Holy
http://www.tankspot.com/showthread.php?56757-Cata-Holy-Priest-Guide-%284.0.3%29
http://elitistjerks.com/f77/t110245-cataclysm_holy_priest_compendium/
http://wow.joystiq.com/2011/01/03/spiritual-guidance-holy-priest-101-part-1/
Builds - There is another post about this.
Note* lightwell has been overhauled and is now a good tool (if we could just get our raiders to click on it rather than run to it...sigh)