Let's start at the end. If you're looking for a new Android phone, go look at the Samsung Galaxy S9. It's about as good as Android handsets get. If you're an iPhone person thinking that Apple has let you down recently and you're thinking of switching to an Android phone, go look at the S9. If you take lots of pictures in low light (in restaurants, bars, clubs, etc.), yep, you guessed it, go look at the S9. If you have been dreaming about a phone that delivers super-slow-motion video, again, go look at the S9. For everyone else, the new Samsung Galaxy S9 is a nice to have, not a need to have.
Both the S9 with its 5.8 screen and the S9+ with its larger 6.2 screen feature Super AMOLED technology. The image quality is out of this world, and measuring by technical specifications, they are the best screens ever put on a flagship smartphone.