I'm surprised my phone picked it up like it did, but this is pretty accurate on the lighting difference. It doesn't show the text crispness/contrast difference though. The PW4 text seems slightly softer. This was both on 17 Light Brightness. The PW4 has a warmer color.
I can match the brightness of the PW3 by turning it up quite a bit more, but it slightly washes out the text.