Interpolation

To test whether the "6M pixels" make a difference, I took 2 pictures, 1 at 3648 × 2736, 1 at 1280 × 1024, both in bmp format. The big one was a whopping 29.9 MB while the other was 3.9 MB. I've cropped both here.

6M pixel one:

Small one:

They look the same to me.