Some of the smaller differences are follows. Command line options are slightly different - type 'mozilla --help' on Linux, type 'mozilla -h > foo.txt' on Windows. Process management is different, Linux Mozilla uses a number of processes where Windows Mozilla starts with one. Process adoption is different: on Windows starting Mozilla twice results in one instance; on Linux starting Mozilla twice results in two instances.
For developers, Linux is a better place to hack on XUL-based Mozilla applications. It's easier to startup and tear down Mozilla on Linux than it is on Windows. Mozilla on Linux is also free from some of the confusing behaviour that many Windows programs have. It's never necessary to clean up zombie Mozilla processes on Linux, or reboot the box after a heavy hacking session.
This was first published in March 2004