I am not very familiar with Git, but I can offer advice on svn.
I am using svn for my project, but only for the code and blueprints. I used svn on all assets for a while (maps, textures, etc.), but the repository size was growing way too fast. Reason is that is saves a copy of that 300MB map of yours each time you make even a minor change. We’re using a free account on Assembla to host our svn repo.
To save / backup such large files, we’re using Copy (a Dropbox-like: www.copy.com), which has a free “Company” account which allows unlimited storage AND saves previous versions automatically, should you want to undo something.
So I would recommend the following: use svn (or git) only for code and small assets (blueprints, materials, particle systems…), and a mass storage solution for maps and textures.
Also I am not using svn on the editor, because there was a delay whenever I saved anything which was annoying me (and our team is small, so there’s no need to manage locks etc.). But I didn’t experience any bug, should you want to try it.