I am using Nvidia graphics card. I run Ubuntu 16 on virtualbox. Host OS is windows 10. Does it make sense to upgrade the graphics driver in my Ubuntu image running on virtualbox? My CPU also support integrated Intel Graphics.
Please do not install/run proprietary graphics drivers in your guest Ubuntu.
By installing the guest additions you will install a custom virtualbox graphics driver that will make use of your host graphics adapter including 3D-acceleration if enabled.
It does however make sense to upgrade your host graphics drivers because bugs there may also affect the virtual graphics drivers in the guest.