I've just gone through Rob Ainscough's video (thanks Rob !) and, like some other pics/video, I find the daylight a shade darker in P3D than in FSX ? A harder AA or HDR in play ? Now,I use a laptop with a somewhat grainy screen and the issue may be on my side.

 

Getting back to history, 2004 brought us a better dayight than 2k2.

I found a darker bloom effect in FS9 adds depth to the sim that otherwise wasn't there (learned this from Fing). By default FS9 looked too bright for my tastes. I will say that with ENB I used the brightest sky texture I could find to offset the effect. Maybe that's what you'll need with P3D is a brighter sky texture (once REX or others are fully compatible).