The current 15" Pro has an almost 3 year old CPU and Integrated graphics card.
top end has the AMD setup. Its pretty decent. Gaming not mentioned but newer games like say XCOM 2 can run it. check specs for game as always if you want that for a diversion. More laptop friendly offerings run fine. Blizzard for example and Diablo 3 or Star Craft 2. I am in seasonal play in Diablo 3, pushing rifts as best I can solo. It takes a fair bit for me to make it slow down abit. Exploding palm build monk...I set things up right it literally is a screen full of enemies blowing up so some slowness expected.
Video work its not like we get much choice (ie. Nvidia CUDA to speed up post processing in CUDA enhanced applications).
You need to run off house power to use the AMD, not battery. This will be the case with most any laptop with dual video. Most high end laptops have the meh onboard and the good one. All make power the thing that separates them. battery...you get the base graphics. This for a reason....good graphics card will eat up battery real fast.
Mid 15 owner, can't complain about its performance. Video work is FCP (d750 video via ninja 2 recorder for pro-res support). Stills I use DxO (aperture was killed off, went to adobe LR and remembered quickly why I left it years ago and DxO a nice enough home to settle into for me, ymmv).
OP look at haswell versus skylake in google searches. Follow many links...its not the be all end all upgrade its made out to be...if MBP even gets it. Find articles with it in current systems and fly by seat of pants feel as well as benchmarks....benchmark as only references do not tell the whole tale. Some benchmarks will have haswell neck and neck you will find or close enough to be negligible imo.