Earlier quoted context omitted.
The size difference is trivial so there's no real benefit to .7z files. However it's a non standard format so I have to hunt around for what the CLI tool is called, then install it, the look up the options... Sure that's not a huge amount of work, but it just seems preposterous. Like using some 'gopher 2.0' protocol instead of http.
Windows has a GUI client. OS X and Linux have p7zip. And package managers. It's not rocket science.
Compressing a directory is a solved problem with standard solutions. You really should have a reason to push something like 7zip.