I used Perforce for 5 years in my previous project. Now I've used git for half a year. At this time I think I can say with confidence that if I were to choose a free version control system, I would go with git, but if I had the money, I would choose Perforce.
Not necessarily because Perforce or the Perforce tools are superior, but the way I like to do software development, I would benefit more from Perforce.
So looking at just what really interests me, here are the differences, or rather the parts I really like in Perforce and miss from git to some extent.