It is worth noting that there will always be exceptions. In my experience, Google Chrome is aggressive both on a guest OS and a main OS when Virtualbox is running. Even when there's only one or two tabs but it could be an extension issue. (Still I have experienced this with the Chrome variants such as Chromium and Iron.)

There are some software too such as image editors where some editors would delay brush strokes regardless of which OS is hosting the program and then there are programs where regardless of which space is on it, it's as fast as it can be.

The issue of guest OS has been solved. It's in cloud based apps and HTML5. Google Chrome nowadays with the help of the web could even be considered a mini OS emulator while dodging the bulk of singular cloud OS sites through tricking the user into clicking apps that are bookmarks. Maturity is the only thing lacking but considering the time gap between cloud software and Linux software, the cloud has caught up much faster because of the business interest behind it. Of course behind the scenes, Linux would always be a step ahead with things such as hardware compatibility.