Samuel J. Greear did an informal comparison of zip, gzip, bzip2, and 7zip, comparing compression ratio and compression time. 7zip looks pretty good, though testing it on some more varied file types and sizes would be in order.
LZMA, the algorithm typically though of as the 7zip algorthm, memory usage is ridiculous.
This another data point any comparison need to take into account.
(will not be published)
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