LZMA2 is faster for 4-threads, if you compress big file (more than 256 MB), so 7-Zip will be able to split it to blocks. LZMA2 was created for XZ format and it includes changes that are good for that stream compression format. Also LZMA2 is better than LZMA, if you compress already compressed data. LZMA decoder is simple. But PPMd decoder is complex. So now I don't like the idea of PPMd / LZby joviermark - uBoot