Favored Souls only need WIS for offensive casting; CHA only up to 19. Since you can start a base 8 CHA, and have more sp and net the 19 you need (8 +2tome +2capstone +6item +1enhancement = 19), it is not a serious requirement. Most every Cleric will be slotting a +6 CHA item just as well, if not their enhancements as well, and get more use out of a higher CHA than even the FvS. My Cleric and FvS are dead even on CHA investment right now.
So stats needed for both = WIS and CON, assuming both are casters and not melee. FvS pulls ahead on melee because a Cleric still needs to invest in CHA for RS abilities and WIS for spells and sp, in addition to STR and CON. FvS only needs STR and CON. This is ignoring, of course, Wings and 10DR/whatever (or even 15DR/Adamantine!).