I advertise regularly on FB, I haven't on Adwords in a long time... got tired of being slapped. I think the key difference between FB and Adwords is CTR, people are not on Facebook to look at ads so you can expect god awful click-throughs even compared to Adwords. Other than that, pricing isn't bad, just make sure you watch your daily budgets or you could spend an infinite amount of money.
Facebook is better for my niche. I also find Facebook allows me to narrow my target audience by catering to certain ages and demographics. By running multiple ads appealing to very targeted groups, my clicks are very cheap and very targeted which in turn helps my conversions.