The binaries (including debug symbols etc.) are the bulk of that size, and storing all revisions locally will almost certainly add up to non-trivial size for a laptop. Unless git has some kind of magic differencing algorithm specifically executable code and debug symbols, I don't really see a way it could work - that's my rationale.

Of course, such algorithms do exist - Google's Courgette - but I don't think git is using them (I have looked) and doubt they are tuned to e.g. Borland TDS/RSM/etc. symbols.

I have no idea how large the svn repository is - it's stored on a SAN and run on a dedicated server I only interact with via svn. It could be many terabytes for all I know; and of course, my team's project tree isn't the only thing in the full repository.