The title of the post sums up my questions: Is performance better, on average, assuming Ubuntu and Windows are used equally and for the same purposes, when Ubuntu is installed inside of Windows 7 or when Windows 7 is installed inside of Ubuntu using VirtualBox? My gut instinct tells me that because Ubuntu drivers are mostly open source, optimizations could be made when translating the virtual system calls of Ubuntu through Windows 7 that could not be made if it were flipped the other way around, because of the closed nature of Windows drivers. However, this is just a guess, and I have no evidence to back this up. I'm not sure, so I thought it would be best if I opened up this question to the experts of the community. I look forward to reading your responses!