According to the
specs, the IPad3 only accepts video up to 1080. Just for future reference, upscaling 1920x1080 video to 2048x1152 will have no real benefits at all.
For the width it's only an extra 128 pixels and for the height is only an extra 72 pixels. By upscaling, you will not notice the difference.
On the contrary, you will have slightly longer processing/encoding time and the final file size might end up being slightly bigger. IMO not worth it.