I am using two Thunder Bolt monitors with my MB Pro. This allows for many desktops on each monitor whether they be Windows or Mac or both. To switch desktops I just swipe with my Magic Mouse or Track Pad. Nothing has ever crashed and everything is blazing fast… well the exception was the Yosemite upgrade that tried to kill the speed, but I finally fixed that. Also, I was able to keep Adobe Creative Suite for Windows without buying a very expensive Mac version.
More and more I am using mostly Mac software, but there are some exceptions where there is not a suitable replacement for some of my Windows programs.
I highly recommend the Parallels solution. I would not have switched to a Mac if I couldn't do this. Seeing that I have the most expensive MB Pro 15" with a retina screen and the dual Thunderbolt monitors, it was a sizable investment that wouldn't have worked out had I not been able to keep the few necessary Windows program.