A great advantage of VPS, compared to both shared and dedicated solutions is snapshot technology support. A snapshot is a state of a system at a certain point in time. It works like game saves in your favorite computer game. If a game is not going well, you can exit and start from a checkpoint. A snapshot works the same way; if you need to go back in time, your system can be restored from a snapshot to its previous state. It is extremely useful in case of a system failure or simply if you run complex tests and wish to save your progress. Unlike a backup option that copies the whole system each time you run it, a snapshot contains only changes. This means that a snapshot takes less space than a backup and can be created/restored quicker. It does not mean that you do not need backups though. Backups are still life-savers in case of operating system failure. Don’t forget to store them externally.
You also get the following benefits:
Yuriy Gandyak:
A VPS doesn’t just have more RAM, disk space, and a  proprietary share of CPU than a shared account. Depending on the provider, some VPS plans offer burstable memory, which is a pool of RAM set aside for extraordinary events. This is the stuff that can help counter the so-called “Digg-effect,” that much-whispered about occurrence that’s the simultaneous hope and fear of everyone who runs a web site. When you have an unexpected high traffic event, burstable memory will call on a pool of reserved, shared memory to satisfy the needs of temporary high traffic. This is not available on shared servers and, while the necessary memory is available on a dedicated server, your site might not get the kind of traffic on a daily basis to justify the expense of a dedicated server. Again, not all VPS plans have burstable memory, so ask your provider if their VPS plans do.