So in summary exporting from RCX 2048 MPEG4 at 32 Mbit per second is the best for iPad3.
Second best is making 1920 x 1080p H.264 at 15MBits/sec but we need to watch what we use to export it from. May produce Moire.
RCX will export from RAW so it will debayer perfectly smooth.
However taking it from already exported to 2048 and than making it into 1920 I will not do.
So again, keeping RAW originals at 5K is wise thing to do, you never know what you will have to export it to.
We may end up with QHD screens having 3840 pixels horizontal, I hope this standard will never happen.
I will test iPad3 playing 2048 sample to Sony Bravia 65" via ApleTV box connected to Bravia via HDMI at 1920
I want to see if ApleTV will accept 2048 and if it will what will happen with 2048 sample with over imposed lines one pixel apart.
Something is going to blew up here...:-)