I think the difference is that domains are perceived as extra. A cleric has his normal spell slots which can be converted into healing spells, etc AND his domain spells which serve to differentiate him from other clerics.
A favored soul, OTOH, has a single list of spells that have to both serve his general purposes and have to serve to differentiate him from other favored souls.
The sorceror analogy is quite useful in this regard. NPC sorcerors vary widely in terms of their selected spells. One may have the standard magic missile/fireball/cone of cold/disintegrate blaster loadout. Another may have ray of enfeeblement, ray of exhaustion, waves of fatigue, and enervation. However, PC sorcerors can't afford to end up totally useless if they run into undead or constructs (as the latter sorceror would be). So they tend to gravitate towards a selection of spells that is applicable to a broad variety of circumstances. Of the sorcerors I've seen, I've yet to see one that failed to take fireball or magic missile. Consequently, PC sorcerors tend to be less differentiated from each other than NPC sorcerors. I would expect the same thing to be true of favored souls.
Then again, other than healing, the cleric spell list has far fewer "generally useful" direct damage etc spells than the sorceror. I would expect that effective Favored Souls would have to pick one or two narrow areas of focus and become very skilled in those specialties. One focussed on melee might take Bless, Divine Favor, Shield of Faith, Lesser Restoration, Resist Energy, Magic Vestment, Prayer, Divine Power, Freedom of Movement, and Righteous Might with a few curative and offensive spells tossed in around the edges. Another might focus on buffing and take Bless, CLW Shield of Faith, Aid, Shield Other, CMW, Magic Vestment, Magic Circle vs. evil, Freedom of Movement, Recitation, Bear's Heart, and Heal. Yet another might choose to focus on curses and take Doom, Sound Burst, Spiritual Weapon, Bestow Curse, Blindness/Deafness, Cure Critical Wounds, Recitation, Slay Living.
However, if the favored soul wants to fill the cleric's role in the party rather than taking on a specialized role, his spell selection will be remarkably predictable.
Domains are an extra that a cleric can use to customize his party role but that don't impair any of his main class abilities. The favored soul's spells known define his class abilities. Consequently there will be much less differentiation within any given role among favored souls than among clerics.
Mercule said:
So, it's good of the desiginers to provide a boatload of domains, the choice and differenciation of which depends upon the player; but it is bad of the designers to provide a double boatload of spells, the choice and differenciation of which depends upon the player.
You're sounding a bit conflicted here. What am I missing about your position?