This is strange to me too. I'm also choosing at the moment between 15" and 13" because my budget is limited. Hence I've asked in this thread:
https://forums.macrumors.com/threads/1102149/
for someone to show me FPS numbers(World of Warcraft,I do a little gaming

) on the 13"/15"(6490M) and heating issues. Guess what!?..there is still nothing on the 15",not a soul. Could this model become the worst selling Macbook Pro ever?
My point is that nobody is willing to purchase this lower end model. My criticism goes to Apple:
Why did they made so much difference in GPU power?!

Never mind the VRAM numbers 256MB Vs 1024MB....look at the bus: 64 bit vs 128 bit, I mean I'm not complaining because my budget is tight......but come on...I know that I can buy the 13 higher end and buy myself a dissent gaming PC for the money difference to the 15" model(higher end). My point/question is:
Is it wrong to want a dissent 15" Macbook Pro for 1800 Euros,or you will have to spend another 400 Euros just for the word(dissent).
Cheers.