The difference is in the intention of the blocking. Intention of the firewall is to block all your access to the content. Intention of the paywall is to encou

The difference is in the intention of the blocking. Intention of the firewall is to block all your access to the content. Intention of the paywall is to encourage you to pay for the access to the content. The difference is also in the legal framework, especially for the people in China in case of the Great Firewall. If you pay and pass the paywall, you have not done anything wrong in the eyes of the Chinese law (assuming that the content was not blocked by the Great Firewall). Passing the Great Firewall might get you into the hot water.