If Facebook were confident that they make a better product, they'd embrace competition as a sort of self-check in the system. They'd spend a day or two to adapt their already-developed you-can-download-your-whole-account feature to allow customers to switch to Google+, if they desire.
But they won't do this. Their reluctance underscores their belief that they don't make a product superior to Google's; if they did, they'd have no problem with these advertisements.