Both SharePlug and VPN can be used to access shared folders on the remote network.

However, under VPN, your device becomes a part of the remote network. Hence, it allows your device to use any network resource including but not limited to shared folders as if your device is physically connected to the remote network.

In contrast, SharePlug brings one of the computers on the remote network to your current local network for only one purpose, i.e., accessing its shared folders. You cannot use the connection between SharePlug and the remote network for other purposes such as sending emails or accessing internal company groupware.

Such fundamental difference, i.e., becoming a part of the remote network for all purposes (VPN) vs. attaching one of the remote computers to the local network for one purpose (SharePlug), affects security and usability.

For security, if your mobile device is lost or stolen, and a malicious hacker got hold of your VPN access credentials, all the computers and systems on your remote network are exposed. The hacker can attack any one of them and compromise the security.

As SharePlug only exposes one computer for just one purpose, it minimizes the risk of other computers being attacked by a malicious hacker.

For usability, VPN is for providing a connection and that connection can be used for any protocol or service. Hence, VPN does not usually provide special helper tools or functions for a specific protocol. Also, since VPN needs to support broad range of protocols, configuration may get complicated or require deploying additional hardware.

SharePlug is for just one purpose, i.e., accessing shared folders. So, it includes handy tools and functions for that purpose. For example, SharePlug has an option to automatically map shared folders when a connection is established, and un-map after disconnected. When a shared folder is mapped, it can be used like a storage card, i.e., you can directly open from or write to that mapped folder.