If you are familiar with hosting control panels, shell commands, and you have basic server administration and troubleshooting skills, then unmanaged VPS is the way to go. Note that while you purchase self managed VPS, you should be capable of managing applications, software, services installed on your VPS. Also, you must know installation/uninstallations, resource monitoring, server performance tweaking and troubleshooting of any technical issues.
“After having shared hosting plans with other providers for many years, I switched all of my sites to Liquid Web a few months ago for my first VPS experience. It's been smooth, fast, and easy to use. At one point I suddenly ran out of disk space, and within minutes I was able to use their system to upgrade my plan and move my site to a larger partition.” – David K.
I can’t say it as a disadvantage of VPS hosting because many of our VPS hosting customers have server administrator to manage their VPS and they manage it in very efficiently manner. But this doesn’t everyone must have server administrator, we have content-rich knowledge base on VPS hosting for our self-managed customers.Also, a managed service option at very affordable price.