I Would like to give my recent update. All my apple devices including MBPR and iPhone 6 are now stable connected to my 5Ghz router on a 40Mhz bandwidth at full speed. As I mentioned about draft wireless in a previous post they are not finalized. apparently Even after updating my wifi routers the updates were not taking completely and some updates included new updated draft drivers for the wifi radios.
So with one a simple reset to defaults fixed the issue. The other one required what's called a 30/30/30 reset. You can Google this for more information.
After fixing the routers and having the wireless card replaced in the MBPR everything has been stable and working great. I was able to change my bandwidth to auto 20/40 and the laptop connects on 40, or specify 40 only and it works. The iPhone 6 is now fast, contact and not dropping.
So in my opinion if the iPhone 6 is using the most updated latest wifi chip drivers but my routers were not because the firmware update didn't aply it correctly and needed a reset. Well I beleive this may have been the issue. Maybe the router companies assumed he firmware update applied the new drivers but in reality the router needed a reset to apply these changes and not just a restart. So now I'm not forced to use my own recommend work around of being on 20MHz bandwidth and all is working.
So if my prevoiuse work arrounfd didn't work for you then you can try this one that corrected all my ios wifi issues. And also since my last post my girlfriend from California has moved in and also with 2 additional iOS devices on my network. Another phone and an iPad Air both on 8.1 and she streams a lot of TV and Movies and has not had an issue.
NOTE: the defaults or 30/30/30 will require you to out all the wifi setting back, reset the default password and add wifi keys. So you will want to make a note of all your setting and you will also want to know your default passwords that can be found in the online manuals for your wifi router.