Six of one, half a dozen of the other
I've used both P4 and GIT and my preference is to Perforce. Git does everything, absolutely everything, including things that should never be done. Very common activities become a struggle with Git's cryptic commands and terminology that usually end up like the XKCD comic says. There's nothing like having Git put thousands of conflict markers in your new code because it didn't quite get the right options. Perforce makes easy things easy so screwing it up takes a bit more effort.
The other issue is shared libraries. Perforce can push and pull a consistent snapshot of many repositories at once. Git can't, so it's pure hell when multiple people are refactoring code across multiple repositories at once.
I've seen nasty bugs in both so I have no preference on stability.