AP or HP Soraka?

HP.

As a soraka you'll be focused first and foremost as long as the enemy aren't potatoes so you need survivability. Also when you play tank soraka you have the advantage of being able to get a warmogs so that's a big advantage for your team.

The heal for hitting enemys with q is a flat amount and her w costs % max health. If anything you need lots of resists and hp regen, not flat health.

Both are strong. Ap raka is when you are a god at landing q's. Hp if you seem to have trouble landing them so you get a warmongs and 3k hp to heal up.

Hp, but usually her items are just utility. I havent played her for a while but if I did it would probably be: (If the game went this long)

I prefer AP.

My standard build is something like. and a situational item.

against heavy burst AP comps and we have them shoved into their base. against heavy burst AP comps and it's even/we're losing against low engage comps that i can poke all day. if i'm being heavily targeted. If i find that my team mates need constant saving and are always getting caught out, the movespeed from it combined with my passive and other MS items allow me to get there on time. If it's a squishy comp that has little to no MR. If i'm ludicrously rich and want to end the game quickly. if my team has a huge split push threat and we're trying to 4-1 push.

I play her as an annoying lane bully. I position aggressively, max Q, and zone the enemy AD carry from farming with my Q. I fed a CRAP ton of games learning this style but once you can dodge etc. with your eyes closed, you'll never lose another lane. You aren't punished for not maxing W because your carry never takes harass in the first place. Because of your positioning, they're forced to harass you. Of course their harass is wasted because you just heal up off your Q anyways. This style requires you to be good at landing Q and good at anticipating enemy abilities but if you get that down you become unstoppable. Those Q's freaking HURT in lane and if you're building AP they're gonna hurt even more in a teamfight.

Any time my ally is losing a trade after laning, i fly in with my passive+MS, then typically i'll E-Q-W-W-Q. If needed i'll R of course but i never use it unless they're going to die. Your E makes for an easy Q since they can't dash, the slow from your Q almost guarantees a root, by then you've gotten off a few heals and your team mate is free to go back in for the easy kill. Even if they aren't rooted, your slow is going to mess up their dash when they step out of E. Making for another easy Q. Because it's maxed you have the 5 second cooldown and a super valuable 50% slow. is core to this build and i never upgrade it to because the MS is just too valuable. You can use it to get in range to your ally if they're losing a fight, chase an enemy if you've turned around a fight, engage with your team is you lack reliable hard cc, peel for your team if you need to escape a bad situation, or my personal favorite...to kite an assassin who thinks they've caught you 1v1 in the jungle and kill them. Her QEQ is absolutely crazy with AP.

345 base damage when maxed out with 35% scaling is going to give you 394 damage off just alone. Add in another 100-200 damage from E depending on what level it is and you're looking at about 888-1088 damage from QEQ. AND you're healing yourself while landing those Q's if they have managed to get a few hits on you....so...yeah...that's why i prefer AP raka.