Either. What is the one that you feel most comfortable with? With a VM you really don't have to worry about drivers, as the virtual machine uses "generic" hardware for the virtualization. You might not get all the full functionality of specific hardware, but it let's you play around with the new operating system to see what it is like.
Dual booting, you need to make sure that there are drivers for the new OS. If W10 has all the drivers included for your device, it is nice to see how all the fun and interesting things that are specific to that device works. Sometimes you can 'cheat' and use the W8.x drivers if you are missing a driver or two. The problem is that you might run into a bug that driver specific, and you'll have to wait for an updated driver to see if that fixes it.
But to help with the process of polishing off the OS it is better to do dual boot, imho. As any errors will be auto reported back to Microsoft, and if there is a hardware/driver issue, then Microsoft will notify the manufacturer.