On the iPhone 6 Plus, Raymond Soneira:
Based on our extensive Lab tests and measurements, the iPhone 6 Plus is the Best performing Smartphone LCD display that we have ever tested. It delivers uniformly consistent all around Top Tier display performance. The iPhone 6 Plus is only the second Smartphone display (LCD or OLED) to ever get all Green (Very Good to Excellent) Ratings in all test and measurement categories (except for Brightness variation with Viewing Angle, which is the case for all LCDs) since we started the Display Technology Shoot-Out article series in 2006, an impressive achievement for a display. The iPhone 6 Plus has raised the bar for top LCD display performance up by a notch. See the main Display Shoot-Out Comparison Table for all of the measurements and details.
The iPhone 6 Plus matches or breaks new records in LCD Smartphone display performance for: Highest Peak Brightness, Lowest Screen Reflectance, Highest (True) Contrast Ratio, Highest Contrast Rating in Ambient Light, most accurate (pure logarithmic power-law) Intensity Scale and Gamma, most accurate Image Contrast, and the smallest Variations with Viewing Angle for Brightness, Contrast Ratio and Color. Where the iPhone 6 Plus display does very well but does not break LCD performance records is in: Resolution (1920×1080 versus 2560×1440), Pixels Per Inch ppi (401 ppi versus 538 ppi). and Absolute Color Accuracy (3.1 JNCD versus 2.1 JNCD).
The iPhone 6 was not as good. Compared to the Galaxy Note 4:
Both are impressive and excellent displays with great state-of-the-art display technology. We recently gave the Samsung Galaxy Note 4 our overall Best Smartphone Display award, and for the time being that continues for all of the reasons originally mentioned there. In particular, for implementing Color Management to provide multiple Color Gamuts, and then using the Color Management to provide the Highest Absolute Color Accuracy for Standard (sRGB/Rec.709) consumer content of any Smartphone or Tablet display that we have ever measured (in one of its four available screen modes, which many reviewers seem to overlook). As we discuss next, dynamic Color Management is something that every display will need to provide in the future.
The iPhone 6 Plus is the best mobile LCD according to Soneira, but the Samsung Galaxy Note 4 is the best smartphone display, LCD or OLED, period.