It really depends on the type of crowd you're targeting. Disqus is pretty decent. You could choose to opt just for Facebook comments taking into account how people are almost always connected to Facebook on their PC/laptop or through mobiles, plus it'll work better if you're planning on promoting on social media. However, not everyone wants to share their FB profile for a simple comment, so take that into account.
With WordPress comments, you can build an email list for future use.
It would also depend hugely on the niche you're targeting. If your blog is more value/content centric, go for regular comments. If you plan to use the blog as a way to add credibility or just plain market it to the world, Facebook.
Hope it helps. Cheers and all the best.