I can tell you that .bz is quite a bit faster and appears to use a more efficient algorithm that zip. The files are, on average, 20% smaller (depending on what you are compressing, a LOT smaller). For pictures, though, I'd go with .lha. Works really well with .jpgs but is less efficient with coding. It tends to be a matter of what you are doing. .zip is a good, all around compression program, but is almost unused outside of Windows. Not sure why except that a lot of linux, unix, BSD and other POSIX based systems programmer have a jones for all things Windows.