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Tar contains a few options to compress the tar-ball. It depends on what compression packages you have installed. I have long known that LZMA is good for making small packages when I can spare the time. For everything else I use BZIP2. Fortunately curiosity has led me to do a small comparison.
More about the Graph.
Compress and uncompress times are in relation to one another, thus they are comparable, as well as /tmp/etc and /tmp/bin.
Size is the ratio of compressed-tar-ball to the disk space as reported by du. It is then adjusted to fit within the ratio, /tmp/etc and /tmp/bin are comparable.
Data for /tmp/etc was copied from /etc with
cp -r /etc /tmp/etc. Same thing for /tmp/bin.