QFT.
But it's a double thing.
Being a learned pianist myself, I was always mildly annoyed that my teacher never taught any interesting songs. So I tried to play Coldplay. Jumping straight in the deep end left me struggling to read it, but it helped my sightreading tremendously for my lessons, and I enjoyed what I was doing.
Truth is, I didn't become the pianist I am by playing For He's a Jolly Good Fellow, nor by playing Lovers in Japan. I got skill by playing both. And practicing. Lots of practice. The easy songs like Jolly Good Fellow taught me how to read music, how to play something correctly which I've never heard before. But playing Coldplay helped me to understand what I was hearing with what I was playing, because I knew the song off by heart, and I could emulate the rhythm without needing to read the rests. After a while I began to appreciate music as an art, not just entertainment, and I didn't have a problem with playing the songs I didn't know.
At the end of the day it boils down to practice. Take sbomb for example. Different folks, different strokes. But I'd definitely recommend starting easy. Don't jump ahead of yourself or you're likely to get frustrated and stop working at it.
That said, Lovers in Japan is fun to play and pretty easy. ;)