truegenius :
which is best compressor in terms of:
1.compression
2.compressing speed at high compression
3.decompressing speed
4.features
1. PAQ is the best, it won many awards.
PeaZip features latest PAQ versions, while KGB Archiver and RK Archiver uses older versions of PAQ.
Anyway, this point is not really relevant if you are going to compress multimedia, as it is already compressed with lossy protocols, specialized in getting better compression/quality ratio for that type of file.
2. Speed and compression ratio are two opposite goals.
It is not much a matter of compressor, even if an implementation may be more efficient than another, but mainly of what compression format you will use.
On most benchmarks most efficient compression at "usable" speed is with .7z, .arc and (only for some file types) .rar and .zipx.
But if you are going to work on an huge backup, you may find .zip speed/compression is more reasonable, while working on small files you may also spend some more times for .7z at highest compression settings, or even .paq.
3. As for point two, generally speaking speed does not cope well with high compression
Anyway amongst strong compressors .zipx generally seems the most inefficient as for decompression speed while .7z and .rar behaves well, see i.e. this benchmark
http/www.peazip.org/peazip-benchmark-3.html
4. It depends on what features you are searching for, most common formats has built-in support for encryption, while only .rar and .arc supports recovery records.
It should not be confused with feature set offered by compressor software itself, i.e. number of supported formats, routines to convert archives, or to save backup scripts, a good file manager etc.