Default [Q] Incredible slow, frequently frozen Xperia SP - What to do..

Hey guys,

I've upgraded from a Xperia Arc to a Xperia SP, hoping for a speed upgrade, going from a 1.0Ghz single core to a 1.5ghz dual core. (a Z(1) was not an option). Strangely, out of the box, the thing felt kinda slow/laggy but I thought "let's give it a try".

Now almost two months later, things haven't been any better. In fact, it regularly freezes completely and while writing this post, I can't even turn it on anymore. I closed the screen, but it doesn't goes on anymore (with 83% battery) .. But that's a different issue.

I'm really hoping what could fix this issue. I'm preparing for a factory reset, let's hope that fixes everything. Yet I'd ask: What more can I do than a complete factory reset. (Does it matters doing a factory reset from inside the phone (@ options > security/storage), the boot loader, or when it's connected to my PC?

I hope someone knows a solution!


Wish I could upgrade to Cyanogenmod, but that would void my warranty (right?), which is absolutely not an option.

Thanks!