Compressed files like zip are very easy to handle, others are more difficult since they need special apps to decompress.
7z is very popular, and xZ gives people some headache in order to find the proper tool.
With xZ you can get an app that does not only xZ and 7z, but also a lot of other format. In other words, if you get this app you most likely don't need anything else to decompress archived and compressed files.
If you need the one-in-all app, stop looking, you just found it!