Parallels on a Mac lets you install Windows on the Mac so you'll need a Windows license.  Once installed, you can start a Windows session either full screen or as a separate window.  It's fully compatible with all Windows software because it is real Windows you are running.

When running Windows as a window, you'll have separate windows on your Mac and you can cut and paste between them.  

It's the best of both worlds.

Be advised that QB recently set a limit on the amount of a check that can be issued to $2,999 using the Bill Pay feature of QB Pro for Windows.  This was done on July 6th with only a day warning.  I bring this up only because it's a huge deal for a lot of QB small business users.