I hate to say this, but Favored Soul is probably, overall, the best one, IF you can qualify for it. Monk Saves, Cleric Spells, weapon specialization? It's easy to take Divine Power, Righteous Might, a god whose favored weapon is a longspear, a greataxe, or a spiked chain, and kick butt.
For this class, Power Attack and Divine Might are awesome feats, because you have to boost your charisma anyway. Consider also a couple levels of Paladin to get a saving throw boost, even though you don't really need it.
As soon as you get weapon specialization, you hop into a PRC, because the spell improvements are way better than the class abilities. Divine Oracle and, if you play in FR, Divine Disciple are GREAT choices for you.
Spirit Shaman is also particularly ridiculous, as there's a cracked combo in it that rules. You take Spontaneous Healer AND Spontaneous Summoner, and memorize any other spells you want.
Warlock is VERY powerful, but I hate it. I hate it for the same reason I hate Marshall. These mechanics are really stupid and do not function like anything else in the game. If all the other classes have spells, why the heck do we need THIS stuff? It adds new SETS of rules, and doesn't modify existing ones. I consider the Warlock and the Marshall mechanically unnecessary, though I have (Somewhat miserably) allowed them in my games.