Format file and compression parameters

I’ve exported unstructured grids to xml files in ascii, binary and appended format. I’ve used LZ4 and LZMA compression with level 5 and 9.

All exported files in ascii (zlibcompression, default option) have a size of 691 Mb. If I exported in binary and appended (zlib compression) all files have a size of 216 Mb. If I used LZ4 or LZMA compression with 5 level, both formats (binary and appended) all files have a size of 180 Mb. And if I use the same compressions with 9 level all files have a size of 180 Mb too.

First of all I would like to know the diference among binary and appended, specially in relation to size files and speed of writing.

Moreover, I would like to know the diference among compressions LZ4 and LZMA.

Thank you very much