Background: Had trouble with low pwm LEDs years ago, set up my workplace to not strain eyes - all good for 2 years now (on windows). Got a new 2018 15" MacBook Pro few weeks ago and eye strain / brain strain /general stress etc returned.
The method: Connect the various Macs with one and the same external monitor (mine was BenQ bl3200 2560x1440) and compare one and the same BLURRED picture on it. I used the default high sierra background on the lock screen.
1. This is the shot from my new 2018 MacBook (Radeon Pro 555X) - using this on the native screen and on externals causes strain within minutes. On the external monitor it shows fever color banding = more aggressive dithering going on. https://imgur.com/LeUhZEY
2. This is a shot from late 2013 MacBook (Intel iris pro) - as you can see the color banding more (esp in the upper blue-ish regions) - and this machine is fine. Colleague lent it to me and I have been using this for a day now and this does not feel any different than my main daily windows machine - so all good. https://imgur.com/vzvH5nI
Also side note: Difference was more visible irl + when taking pics of the screen with the phone - use a camera app with a manual focus ability - that way you can avoid contaminating the picture with moire noise from pixel array.
Also a side note. Didn't have this kind of forum years ago when first hit with computer eyestrain. So really thankful for the founders of this for setting this up and everybody who shares their stories and ups and downs. Keep up the fighting!
Cheers and happy autumn!