After you have done this, other Internet access is still prohibited until explicitly set up. This might seem a minor difference, but it makes a major difference. Socks allows you to be sloppy. With a poorly set up Socks server, someone from the inside could gain more access to the Internet than was originally intended. With the TIS toolkit, the people on the inside have only the access the system administrator wants them to have.
Socks is easier to set up, easier to compile and allows for greater flexibility.
The TIS toolkit is more secure if you want to regulate the users inside the protected network. Both provide absolute protection from the outside.