Other VM programs don't control VTx/Hyper-visor until they are run, seems logical right? Well that isn't Microsoft's style. I just switched to Hyper-V and I find myself having issues that I didn't have in VirtualBox. But I'm determined to learn Hyper-V, in the mean time its nice to be able to easily switch between programs.
Here is how I do it, requires a reboot, but doesn't require you to do anything during reboot like some peoples alternatives.
I created 2 Cmds, one to enable Hyper-V to auto take control of Hyper-visor *it needs to control it from boot or it won't work* and another to stop it from auto taking control. This allows you to simply reboot and run VirtualBox or whatever then reboot and run Hyper-V without tweaking settings or uninstalling anything.