2013-07-24. I just downloaded and compared 7z930.exe(alfa)(2012-10-26) vs WinRAR_Portable_4.10_32-64_Multilingual.paf.exe(2012-02-05).
The comparison result: Firefox.ratio = rar.size 77402065 bytes / 7z.size 71965613 bytes = 107.554235659745%
However the wourld best free archiver 7z has not function of timestamps saving:
modification time for dirs, and creation (+ access) time for files and dirs.
My favorite order of sorting+viewing for files+dirs is creation time, so I avoids use 7z yet.
But unlike Rar, 7z is universal archiver as on Win7-32-ultimate as on Linux.
Does 7z930a restore exact timestamps (write & create & access) for files & dirs?
7-Zip can store full NTFS timestamps in 7Z and ZIP archives. ZIP archives get full timestamps by default; in contrast, only modification time is stored in 7Z archives by default. There is a command-line switch (-tc, please refer to the manual) to override these actions. All available times are restored upon extraction (if the file system supports that). I tested 7-Zip 9.30 alpha for x86 Windows (not a standalone version).
Be aware that if you are compressing files from the command line, the directories that do not match the wildcard are not stored explicitly, nor their timestamps are.