Again, you are wrong. This was said in the DisplayMate link about the Galaxy Note 5 screen.....
More importantly, on the Galaxy Note 5 the Maximum Brightness can go much higher when Automatic Brightness is turned On, so that users can’t permanently park the Manual Brightness slider to very high values, which would run down the battery quickly. High screen Brightness is only needed for High Ambient Light, so turning Automatic Brightness On will provide better high ambient light screen visibility and also longer battery running time.
Even the Galaxy Note 4 i had earlier had 750 nits in brightness when the 'Auto brightness' mode was used. This was said about the Galaxy Note 4's brightness from DisplayMate.....
When Automatic Brightness is turned On, the Galaxy Note 4 reaches an impressive 750 cd/m2 in High Ambient Light, where high Brightness is really needed – it is the brightest mobile display that we have ever tested. As a result of its high Brightness and low Reflectance, the Galaxy Note 4 has a Contrast Rating for High Ambient Light that ranges from 100 to156, the highest that we have ever measured for any mobile display.
So if you believe that the Galaxy Note 5 screen are worser than the Galaxy Note 4 screen, i'm afraid you are totally wrong.
And i have been looking at an iPhone 6 Plus with the brightness at max outside in sunlight and compared it to my Galaxy Note 4 and the new Galaxy S6 edge+ i have now. The iPhone 6 Plus doesn't even comes close to be as bright as the Galaxy Note 4 and Galaxy S6 edge+ is. Not by a long mile.
EDIT: The iPhone 6 and 6 Plus does have 550 nits in brightness according to DisplayMate as you can read here:
http://www.displaymate.com/iPhone6_ShootOut.htm. So their measuring is correct between the different phones out there.