Because of your comment, I did a quick google search and pretty much every source says that .tar.gz is also pretty ancient and not that good (from a compression point of view). For better compression, you can use the xz or 7zip formats. The former is more used on Linux, if that's what you're using.
Yep, but Windows is still the majority right now... And i'm sure there are a lot of people out there that don't have 7zip installed (why doesn't MS include their own implementation already ?)
People barely understand how to open a .zip file, explaining what .tar.gz is and why you need an additional program (on Windows) is going to be impossible.
I tend to prefer zip because of cross compatibility with Windows with no extra software needed, and because the Windows software to unpackage a tar.gz that I have used required unpacking it twice (once for the gz, then again for the tar). It seemed like a hassle.
On Linux I command line everything, so they are the same to me, so I have no preference there. But is there something actually better about it?
With .zip you can extract just one file from it, while with .tar.gz you have to uncompress the whole .tar before you can get the files - so that's worse.
But, since you're compressing all files at once you could get better compression since information can be shared between files.