Where the heck did you get the idea that I think git stores diffs? All I'm saying is that Git's merge support is useless for binary files, because it doesn't know anything about them. It'd be great if I could have git show visual differences in STEP files, but it doesn't do that, so merging is at the file-level, not content-level, so it becomes no better than what subversion has.
Now pray tell how much will I pay and how long will I wait when I want to check out 20 megabytes worth of drawings at customer's site, running through a 3G wireless modem - a common scenario for me. The repo is a couple gigs large in the current revision, and has the overall size of about 100G.