For 3 yrs till last month I had Elitebook with i5, QuadroFX 1000M, 4Gb ram, 2x SSD and a good lcd panel in it - I gotta say, that laptop was from 2009 and it handled photoshop awesomely.
Now I switched to MBP 2015 with dGPU Ati R9 370X 2gb and the result is not so huge - quite disapppointed. However, MPB offers me more things I am really content with. Very SAD fact that laptops with 2009 x 2015 year difference -> 6 years and the performance is not so noticable. On the other hand Adobe is too lazy and is to blame, they make heavy applications not so optimized in terms of performance. Current LR Classic is a nice step forward but... I have a f... expensive laptop from 2015 and I dont see it flying in Photoshop.
Apple should finally wake up and offer something worth the money to all the professionals and they should provide QuadroFX graphics in their laptops.