I checked out the full repository of an open source project I have been tinkering with in both SVN and Git (libgdx). The SVN was MUCH larger than the Git repository on my hard drive (i think 33% more, but I can't remember).
Another example is Django. A Subversion checkout (only trunk, no branches or tags) uses 186 MByte on hard drive, a Git clone uses 87 MByte. That's really astonishing when considering that the git clone contains 6 years of history and 10600 commits.