I don't know if there's any way of telling whether Google finds Facebook comments on your blog "more engaging" than non-Facebook comments. Google certainly isn't saying.
If by including Facebook comments, you make it easier for your site visitors to engage with your content, that's a good thing to do regardless of what Google thinks about it.
My advice: stop worrying so much about what Google thinks and focus instead of what your human visitors think. Do they
like having FB comments automatically included on your blog, too?