PPTP = Point to Point Tunneling Protocol. Very easy to setup as most devcies today have a native (built-in) client for it. The only drawback is that it does have some security issues.
L2TP = Layer 2 Tunneling Protocol. A more advanced protocol that uses IPsec for security. Most devices have a L2TP client built-in too, so this would be preferred to PPTP.
