I'll chime in to the convo regarding the OS choice...
The large company I work for is completely based on Windows 7. We allow Macs, but the large majority of all users use Windows 7. I also use 1 application that you simply cannot use with Windows 10. Given that Windows 7 is the standard, I had to install Windows 7 on my rMBP. I actually did this last week via Parallels.
I will agree that Parallels is probably the way to go for most regular consumers...however Bootcamp definitely has its advantages as well. My application of Windows is mostly thru Coherence mode or similar. I use 1, maybe 2 apps via Windows and otherwise continue my regular Mac workflow. It's worth nothing those 2 apps are not resource heavy.
For others, whose work relies much more on exclusive Windows app use and more graphics intense programs, Bootcamp is by far the better option. You're always going to suffer performance degradation via Parallels vs Bootcamp. The simple way to look at it: if you prefer the Mac OS and just require the workaround occasionally to run Windows, get a VM. If your work relies heavily in the Windows department or you're reliant on an intense application in Windows, use Bootcamp. Or you could use both...