Or - who is "stricter"?
From what I've read, both flags add extra warnings, not included in '-Wall', but what distinguish them?
-Wextra is about turning on warnings that may be less useful or more of a nuisance (because they may warn about code that is acceptable to the programmer) than other options. It is generally for use when you want to scour your code for issues, make changes to address genuine issues found, and then turn off -Wextra for regular builds.
-Wpedantic is about sticking more closely to the language standard. It warns for some uses of language extensions that the compiler otherwise considers normal but that can make the program non-portable to other compilers.