WinRAR is the program I use because it has the best compression ratio of all archiving programs, and can unzip every format I use. It is kept simple and functional.
That isn't true.
gzip (tar.gz),
bzip2 (tar.bz2), and
7-zip (7z) all compress better than rar. And out of the three, 7z compresses the most, followed by bzip2, and finally gzip. However, another factor to consider is the amount of processing power and time it takes to decompress a particular archive.
In my opinion, if we're talking about downloading files from the Internet on a PC, saving bandwidth is more important than saving decompression time because it saves the host's bandwidth which saves them money. Another positive is the amount the download time is reduced for the user, but the extra time spent decompressing might make them end up spending more time to actually use what's in the archive.
In portable systems running on battery power, it's more important to use compression formats which put less strain on the CPU, because more CPU usage equals more power usage, which equals a lower battery life. The MP3 format is less intensive on the CPU than the Vorbis format using the OGG container.
In games using compressed data, using formats that take longer to decompress will cause longer load times. Some examples of this are id Tech 4 (Doom 3 engine) and id Tech 3 (Quake 3 engine), which both use zip files (renamed to .pk4 in id tech 4, and .pk3 in id Tech 3) to compress their game data. This saves hard drive space and also makes the games very portable.