Virtual Machine or Dual Boot

[dacads]

Right so I need to make a windows store app using visual studio so will need to install Windows 8.1 (uh oh). I am wondering how I should go about this should I install W8.1 onto a virtual machine or onto a separate HDD?

At the moment I have Windows 7

 

[dacads]

I haven't got round to getting an SSD yet

Luckily I have enough internal HDDs..if I go down this route will the HDD need to be formatted and empty?

 

[dacads]

I am using virtualbox, currently installing W8.1