High-DPI is close to useless in Windows, most apps look weird.
I think parallel does a great job upscaling to retina without high-dpi. At least I got jealous when I glanced over to my schoolmates screen which looked a lot crispier with windows than mine. Also the settings of parallels look more promising imho http://kb.parallels.com/Attachments/21793/Images/Screen%20Shot%202012-12-24%20at%202.32.17%20PM.png