Samsung Galaxy Ace 2x VS Sony Xperia SP?

I'm getting my first phone. I'm a 14 year old teenage girl, I will be using it for texting and playing music only, and maybe taking the odd picture. I won't be doing much (if any) video game playing, video watching or Internet surfing on it. I'm fine with charging it every night but it has to be able to last the day without dying, with the screen turned off most of the time. My phone company offers both of these for the same plan, so price isn't an issue. In terms of size I'd prefer a phone that's around the size of an iPhone, though a little smaller is fine as well. Not too heavy. Otherwise it should just be generally user-friendly and not buggy or anything.

Which would you pick? I want to make sure I make the right choice.

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