Compared to Swish-E Indexer?

Swish-E Indexer uses the Swish-E Search Engine, Search files utilizes the Search functions built into drupal core

Swish-E requires the upload module be enabled, I would assume that Swish-E only indexes those files that were uploaded and attached to nodes, Search Files will index any directory on the server Apache has read access to. Search Files can also index multiple directories, not just one.

Search Files also lets you use whatever helper apps you want for whatever extensions, Swish-E limits the types of files you can index.

Swish-E also requires you to have the Swish-E binary installed on your server to do the indexing. Search Files doesn't require a separate binary.

Basically you can search a directories of files and you don't have to have the attached to nodes, just give Search Files the directory and off you go.

Thanks for your answers! You make clear the differences and I think that Search Files has many advantages. I really like the fact that the files don't have to be attached to nodes.

Now if there was only a D5 version...

It looks that choosing swish or search_files depends on your needs.
For me swishs method to walk through the list of files attached to nodes is appropriate. Every hit also offers a link to the node to which the files is attached. Then I can check the node and also have a look at other files attached to that node. That looks for me to be a main advantage. Not having a link to the corresponding node is not meaningful in my case.
On the other side swish maintains an index which is told to be perform well (compared to?) but is based on some binary file (not database).

Search Files was not intended to search files attached to nodes, just if you have a directory on your server with files that you want to be searchable. This is a case that I ran into and i didn't want to have to create a node for each file, or attach hundreds of files to a single node.