I've been doing testing of many compressors to test compression and decompression speed but it seems like you can't really do better than DEFLATE and LZMA2, as far as text is concerned. For example, with my rockyou.txt as a test file, the gzip'ed file decompressed twice as fast as the xz'ed file with the filesize being ~4.6MB smaller on the xz file.
Sizes and decompression speed:
043716819 rockyou.txt.gz 0m2.032s
038785200 rockyou.txt.xz 0m5.409s
032583172 rockyou.txt.tan 3m48.014s
Is it possible to decode as fast as LZMA2 and yet have better compression? Compression speed is not an issue.
.tan is TANGELO 2.4