Both the phones feature impressive looking Full HD + displays with the slightly taller aspect ratio of 18.7:9 and a resolution of 2240 × 1080. (factschronicle.com)
The Galaxy S8 + has a 6.2 ″ display and the upcoming Galaxy Note 8 will have a 6.3 ″ display, though with taller aspect ratios. (xda-developers.com)
The thing is, the iPhone X's taller aspect ratio actually means the screen's total area is smaller. (engadget.com)