SMPP (Short Message Peer-to-Peer) is a low-level, binary protocol that provides high-throughput delivery, typically used by large-scale SMS providers and aggregators.
It is more suited for large-volume, high-frequency messaging and is known for its efficiency and speed.

HTTP (HyperText Transfer Protocol) is a widely used, high-level, text-based protocol that is used for a variety of applications, including SMS.
HTTP API are typically easier to integrate with web-based systems and are more versatile and flexible than SMPP.
They are also easier for developers to work with, as the data is conveyed in a readable format.

In conclusion, if high-speed, high-volume SMS delivery is a priority, then SMPP is a good choice. If ease of integration and flexibility are more important, then HTTP is a better option.