Has no journalling, so preferrably only used for CF and USB sticks, or for very small file systems where journalling makes things worse than better.

No indexing, so don't use for many files.

Preferred choice for external storage, because virtually all systems can read ext2/ext3 (including Windows with proper software).

Has journalling. Is perfect for all-round (server) systems, in particular root file systems and such. If there are many small files, and many files in one directory, this one is not the preferred choice because there's no specific indexing method (or none that I know of).

Has full resize support, so can be used for LVMs.

Is robust: has proven its worth.

Disaster recove  ...