In most cases, your network access is slower through a VPN than not. The exception would be if for some reason the route to the VPN server is faster than the route elsewhere (perhaps your network gives a priority to the VPN server, has a fast connection to the VPN server, and the VPN server has a faster connection to the rest of the Internet than your non-VPN access). That’s because of the additional time to encrypt and encode the traffic within the VPN protocol on both ends, and to pass traffic via the server instead of directly to the end point. Besides for securing your traffic from the being easily snooped by your immediate router/Internet service provider, a VPN is sometimes used to make your traffic to the remote server, appear to originate from the geographical location of the VPN server, instead of from your actual geographical location. This is sometimes desirable, if you want to access services that are blocked by the remote server to your geographical location, but sometimes it can be the other way round, i.e. you get served localized contents that are localised to the location of the VPN server instead of your own location. Up to you to see if that’s a disadvantage. In some cases, aggressive policies on your router/Internet service provider may block the use of a VPN, or limit its use by slowing down your service if a VPN is detected.