Lord Pendragon said:
As always, FireLance, your opinion is insightful and well-written. In this case, though, I respectfully disagree.
Thank you for the compliment

. I still think the half-celestial template is balanced for a paladin at LA +4, though, and I hope I may be able persuade you if I restructure my arguments slightly. Let's look at four basic areas: offense, defense, spells, and other abilities.
1. Offense
The advantage in offense probably goes to the normal paladin. In a normal melee attack, the half-celestial is less accurate but does more damage (as mentioned, the equivalent of power attacking for 2). When smiting evil, the half-celestial is as accurate, but does less damage. Divine Might helps offset this as the half-celestial can use it more times a day and does more damage each time. The half-celestial also gets the same number of smite evil attempts (or one more), but one is the less accurate racial ability. In ranged combat, the half-celestial loses out. The half-celestial also gets his iterative attacks more slowly.
2. Defense
Here, the advantage probably goes to the half-celestial. He gets +1 natural armor and better saves due to higher Charisma, Constitution, Dexterity and Wisdom. He is also an outsider, which means he is not affected by spells such as Charm Person and Hold Person. He usually loses out in terms of hit points, especially if he is low-level or has a high Constitution score (see attached excel file). However, this should be offset against his damage reduction/magic and resistance to acid, cold and electricity. Unless he is always in combat with enemies that can penetrate his damage reduction, his hit points may go further than those of a normal paladin. In addition, he gets spell resistance.
3. Spells
Again, the advantage probably goes to the half-celestial. At low levels, he gets access to more (but fixed) spells such as Daylight (at will), Protection from Evil (3/day), and Bless (ECL 5), and Aid (ECL 7) through his spell-like abilities. One level after a normal paladin gets access to 2nd-level spells, the half-celestial gets Cure Serious Wounds and Neutralize Poison (ECL 9). When a normal paladin gets access to 3rd-level spells, the half-celestial gets Holy Smite (ECL 11). He also gets Dispel Evil (ECL 13) before a normal paladin gets access to 4th-level spells. At higher levels, the half-celestial generally gets one less spell per day of each level compared to a normal paladin, but he also gets access to Holy Word (ECL 15), Holy Aura (3/day) (ECL 17) and Mass Charm Monster (ECL 19). His caster level for his spell-like abilities is also generally higher than a normal paladin's caster level for his paladin spells. The save DCs for his spell-like abilities are also Charisma-based.
4. Other abilities
Here, the advantage is probably to the normal paladin. A half-celestial's special mount is usually weaker than a normal paladin's, as is his ability to turn undead. The amount of damage he can cure with lay on hands may also be lower if he is low-level or has a high Charisma score (see attached excel file). The number of skill points he has may similarly be lower if he is low-level or has a high Intelligence score (see attached excel file), and his maximum skill ranks will be lower. To balance this, the half-celestial can fly.
All in all, if your focus is on offense or the paladin's class abilities, you may be better off playing a normal paladin. However, if your focus is on defense or spells, a half-celestial paladin is probably the better choice. As such, I would say the half-celestial template is balanced at LA +4 for a paladin.