PPTP (Point to Point Tunneling Protocol) is a good, lightweight VPN protocol offering basic online security with fast speeds. PPTP is built-in to a wide array of desktop and mobile devices and features 128-bit encryption. PPTP is a good choice if OpenVPN isn’t available on your device and speed is top priority.
L2TP (Layer 2 Tunneling Protocol) with IPsec (IP Security) is a very secure protocol built-in to a wide array of desktop and mobile devices. L2TP/IPsec features 256-bit encryption, but the extra security overhead requires more CPU usage than PPTP. L2TP/IPsec is an excellent choice if OpenVPN is not available on your device, but you want more security than PPTP.
OpenVPN is the premier VPN protocol designed for modern broadband networks, but is not supported by mobile devices and tablets. OpenVPN features 256-bit encryption and is extremely stable and fast over networks with long distances and high latency. It provides greater security than PPTP and requires less CPU usage than L2TP/IPsec. OpenVPN is the recommended protocol for desktops, including Windows, Mac OS X, and Linux.