Exclamation how to get the best of my screen ?

today i played the same video (youtube video via the youtube app )on the SG4 and my Z and i couldn't tell the real difference between them both but as i know our screen is kicking asses ;/ when i open the same picture on my phone was amazing but not the same way around
anyone knows how to get the best of the screen ? or the best settings for our Z ?

Hit thanks if i helped
Sony Z (c6603) running stock 4.4.4 locked bootloader
xperia x8 running gdx 31b locked bootloader