User blog comment:Fistful of Force/Why I believe dedicated supports are better than AP supports/@comment-24234490-20131130175517

In both the situations you've given Annie is actually the better pick. Soraka's heals will be effected by ignites and don't create any space between your target and the enemy team. In the second situation, Soraka won't be able to outheal Nidalee's spears and your team-mates will still be one shot kills even after a heal. At least with Annie you have the option of flash-stunning Nidalee and going for the high-risk teamfight win. The turret is going down either way if you play defensively, all Soraka is able to do is manage the decline, Annie can completely change the complexion of the game.

Annie's stuns are much more versatile, they prevent damage, create space that prevents more damage and can also be used to prevent channeled abilities with Nunu's ultimate being one example. If used on a character that only has one gap closer after he's used it, that character can't no longer do "any" damage to your team-mate. Annie's stuns prevent more damage than Soraka's heal could ever hope to regenerate and that's ignoring the fact Annie does more damage and is tankier than Soraka.

Soraka is a poor choice in most games, the only unique feature of hers is her ability to regenerate mana for team-mates and doing so puts your only CC on cooldown, so isn't worth doing in most situations. You'd only want to pick Soraka when you're laning with someone with lots of escapes who won't need your CC, who is very mana dependant and would benefit from being able to spam their abilities.