There can be a performance issue, especially if you try to run something like games from your VM. However, if you aren't into gaming, I don't think there is enough performance loss to put in the effort and the risks with dual booting.
I haven't honestly had a true "dual boot" in more than 5 years now. But I have tons of VM, I do everything in VM's these days.
When using a VM you will need more RAM in your HOST computer -- VM's just EAT RAM for breakfast. CPU power isn't usually an issue on a VM (assuming it's a single user system like Windows rather than running a Virtual Server).
However there's ANOTHER advantage you can do with a VM. You can run it in the background which means you don't even have to be logged on to the HOST machine if the VM is started as a batch / system task.
In addition to this a USER can have an account on the VM without having to have an account on the main Host machine -- this can be great when you want remote access to the VM or just for testing stuff where users have different privilege levels etc.
Ensure though that your VM is on a decently fast disk drive -- otherwise you will get a performance hit with "Double I/O" . On an external drive have yoiur images on an e-sata or usb3 drive. Even better if you have a spare SSD - but ensure your VM has enough RAM otherwise you will get a condition known as Thrashing --this is where the machine is simply moving pages (chunks of storage) to and from disks because there isn't enough RAM in the machine. You can spot this condition easily - the Disk I/O Led will be on almost continuously, while the computer will be seen to be doing nothing.
It's even more horrendous if you get "double thrashing" where both the VM AND the Host are short of RAM.
Like Pparks1 I haven't used dual boots for "Donkeys years".
It is, of course, the best to use a SSD for the virtual system. I run every OS from a SSD, even here where I use an external enclosure. In VMware you can only use USB - eSata is not supported. I tried USB2 and USB3 and both work well with a small advantage for USB3. Shows again that the OS performance comes from the fast access time and not from the data transfer time.
I did try a 5400RPM spinner that I had recovered from one of my laptops. That worked so,so. It was still workable but too slow for me.
I've had no problems Dual booting 7&8 on EUFI desktop and regular BIOS laptop, both dual boot systems are on SSDs.
When running 8 on VBox (gave it 4GB RAM, was same as 2GB RAM ) on my desktop, it was noticeable slower than when I moved it to dual boot.
Dave, have a look at this. That is Windows 8 CP booting in vBox. Couldd not be any faster. I really don't see much of a performance hit with my (office type) applications. Maybe for programs where you depend on FPS one would notice an impact.
The old lappy only has 2 GB of RAM, but I never would be running two applicatons/tasks of significance from both systems at once. Do you thing 2 GB would be a problem?
Thanks for any help.