Windows on Mac using Virtual Box has always been the
cheapest & safest Virtualization option.
In cases where you need best productivity its probably better to opt for Boot Camp or a better Virtualizaton tool like Parallels / Fusion to use Windows on a Mac.
For some time Apple introduced Boot Camp which allows you to dual boot Windows (or any Linux/OS) and Mac without loosing productivity.
Currently evaluating Parallel for a trial of 14 days and soon after plan to test out Fusion for a trial of 30 days.
Fusion vs Parallels
There is a price point to consider while using Fusion or Parallels.
In case of using either of the applications, you could perform a dual boot using Boot Camp and point Parallel or Fusion to use the Boot Camp Partition when its needed within Mac OSX.
In case of Parallels expiring, we can install Fusion and convert the Parallel virtual machine into a Fusion equivalent. That way you could evaluate both the virtualization tools.
Once you have evaluated both, consider purchasing the one that works best.
Boot Camp
In case you do decide to install Boot Camp, please ensure you don't delete or format any of the partitions other than the Boot Camp Partition.
Especially the ones which are 100MB (which is the OSX Parition Table) & 200 MB (which is the OSX Recovery Disk) partitions. Both these are necessary to boot back into OSX.
In case you ever have an issue where you have lost your OSX partition and it would boot only into Windows Boot Camp partition, use
TestDisk to recover your partition table.
Credits : Image from MacObserver.com