In computing, RAR is a proprietary file format, a lossless compression algorithm used for data compression and archiving, developed by the Russian software engineer Eugene Roshal. RAR uses a compression algorithm based on the LZSS which, in turn, is based on the LZ77, Thomas James Storer and Szymanski (1982). The dictionary size can vary between 64k and 4 Mb. The RAR is slower than ZIP, but has a higher compression ratio. RAR Another feature is that it has a better ZIP data redundancy. The format also allows what is known as a solid compression for compressing several files together, so that a single dictionary applies to all information, so that the compression is greater.
Bzip2 is a free program developed under BSD license that compresses and decompresses files using compression algorithms Burrows-Wheeler and Huffman coding. The compression ratio achieved depends on the contents of the file to be compressed, but usually is far better to compressor based on the algorithm LZ77 / LZ78 (gzip, compress, WinZip, PKZip, ...). In return, bzip2 uses more memory and execution time.