What difference between dpkg-buildpackage and debuild? What is better to use to build deb packages?
The difference between those two is that
debuild is several tools in one whereas
dpkg-buildpackage is just 1 step in the Debian package building process.
Debuild is a front-end wrapper for
debsign. It creates all the necessary files and runs the necessary steps to build a package, cryptographically sign it, and test it for policy violations and other checks.
You can just use dpkg-buildpackage and the other tools manually to build a package.
What works better depends on several factors that depend on the complexity of your project. If you want to learn more about package building it would better to complete the task manually first. This is only an opinion, to be clear.