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Just a thought regarding the unzipping performance. They are likely to be even (32 vs 64) because the unzipping process is a very low-CPU process. The algorithm is designed to make the decompression much easier than the compression, and therefore you are limited by I/O. You didn't mention whether you wrote the decompressed output to disk or to /dev/null. Of course, making that change would only remove one part of the I/O, reading the compressed file would still be done.
Thanks for the interesting article.