Paladins are not just Paladins. We have many names, Critadins, Waradins, Retnoobs, Clerics, Healadins, Tankadins, the fact of the matter is that we are the most durable class and can adjust to play in any situation, and only you can decide what type of Pally you want to be.
For those of you looking to play a Healadin, Holy is the talent spec to go with. In raids, everyone who can heal, naturally heals. A Paladin fits into this natural order by staying back and healing, and thanks to their ability to wear plate, can be one of the most dangerous healers in the raid group, if they're played well enough. Perhaps reading this guide will simplify for the work you need to extort while playing your Healadin.
Plate Priest, Healadin (30/21/0)
This talent spec focuses on the talent trees, Holy and Protection. The Holy part of things gurantees that you will be far more substantial at healing during raids, and the additional buffs of armor, defense and the new blessings from the protection tree combine to create a build very good for healers who can live out during the raid, and absorb damage. for Paladins very rarely end up using the same build, although many times they are similar. After speaking with many Paladins, it has been easy for me to determine this as one of the premier builds for a Paladin, as the bonuses to Intellect, the addition of two of the most important blessings (Sanctuary and Kings), as well as the Improved Blessing of Wisdom Buff, makes this a great build for a Healadin looking to be very active during raids.
(see this page discussion)
Protection Paladins are excellent at PvP with Reckonbombing, and Improved Hammer of Justice, along with Blessing of Kings(Paladins are divided on this. A lot of people like it, and a lot think it is a second or third rate blessing, depending on class) and Seal of Command. If you store 4 Reckoning charges, use Blessing of Kings and Seal of Command, you can easily OHKO anyone in cloth or leather armor.
Paladin tanking is an interesting thing, and speccing full protection to tank may not be the best thing to do. This is because with improved righteous fury, divine favor, and holy shock, you can put out almost 1000 threat instantly without any sort of +spellpower bonus. This is a substantial ammount, and works almost like a warrior taunt. But with improved righteous fury and Holy Shield, you get a 90% bonus to threat just from improved righteous fury, and holy shield will do some 273 threat per proc. The difference is, a holy build might have a little more trouble holding aggro than a protection build, but a holy build could grab initial aggro quicker.
A retribution Paladin's most powerful talent is Seal of Command. Most paladins have this ability, as it is useful to everyone, since it scales with both +AP and +spellpower. Typicaly, retribution and holy will be taken together in varying degrees since the two trees compliment eachother wonderfully. Particularly, improved judgment is useful to eaither a holy or retribution heavy build.
One question that gets asked a lot is "Should I take divine favor or repentance?" Well, the answer depends first on which ability you like more. Second, it depends on if you plan to mostly PvP or PvE. Repentance is awsome in PvP, but because it only works on humanoids, it is not so useful in PvE, where divine favor is much better.