.tar is Unix-based and natively doesn't compress data (it was originally designed for tape backups in the 70's). If you use TCShell, Bourne, Korn etc. in a Unix environment, then you can use the gzip command line argument to compress a modified version of the .tar format.
There is little difference between compression ratios for .rar (propreity format) and .zip (now public domain) formats - both are extremely robust and support AES encryption.
Personally, I prefer the .7z format used by 7ZIP - it provides custom compression ratios, and on very large files consistently achieves about 10% greater compression, albeit it at a slower speed (greater compression = slower speed).
I regularly use the command line version of 7ZIP within .BAT files to compress data before using ROBOCOPY to backup the .7z files.