We have a number of remote workers around the world that need to share the same files (including adding to and editing).
We have used SVN in the past with great results.
One of the biggest SVN repos we had was 17GB. The size was never the problem. We had all sorts of stuff in there, mainly binary files.
However, the drawback was that SVN stores a hidden folder in each folder is not too user friendly. (Esp when users copy and paste folders).
Git seems to solve this. The question is should I use Git, stick with SVN or is there some other open source tool that I've not come across yet?
If the main drawback you are worried about is the many .svn hidden folders, this is no longer the case as of v1.7.
See Working Copy Metadata Storage Improvements
A key feature of the changes introduced in Subversion 1.7 is the centralization of working copy metadata storage into a single location. Instead of a .svn directory in every directory in the working copy, Subversion 1.7 working copies have just one .svn directory—in the root of the working copy. This directory includes (among other things) an SQLite-backed database which contains all of the metadata Subversion needs for that working copy.