pathlib is the more modern way since Python 3.4. The documentation for pathlib says that “For low-level path manipulation on strings, you can also use the os.path module.”
It doesn’t make much difference for joining paths, but other path commands are more convenient with pathlib compared to os.path. For example, to get the “stem” (filename without extension):
os.path: splitext(basename(path))[0]
pathlib: path.stem
Also, you can use the same type of syntax (commas instead of slashes) to join paths with pathlib as well:
path_2 = Path("home", "test", "test.txt")