How do you handle blog comments on Wordpress?

When using Wordpress, what kind of comment system do you run? Should you use the standard comment system that comes with it or do you opt in for Facebook comments? I've always overlooked this part, but after seeing a few competitor websites, some have Wordpress comments and others Facebook comments. Does this have any effect in the long run? And does one system overpower the other when it comes to ranking? What do you use and how does it affect your money site?