Google offered a bit more in terms of total pay + benefits, but I considered both packages very good and therefore not a factor in my decision.
Here are the main factors that went into my decision:
First, Google has > 10X the number of engineers as FB. By this very fact, and having been in existance for longer, the scope of things Google works on is much larger. On the other hand, FB has a much sharper focus on impact: self-driving cars simply won't get worked on because there isn't enough people and more pressing work needed to be done. This is a matter of taste, and I preferred FB here.
Second, having a family, I was concerned about work-life balance. To my friends to worked at Google, it was now a 9-5 job. At FB all-night hackathons are still very much a part of the culture, however there are lots of people with families there now (especially in Seattle). My FB friends had lives outside of work but enjoyed what they were doing and worked very hard. On the benefits side, FB offers a week more of vacation and 4 months of parental leave. In all, I give Google the edge in work-life balance.
Third, culture was very important to me. I felt that there was a sense of complacency amongst a large minority of Googlers. They worked on large, established products making incremental improvements. At Facebook, I met lots of people fired up about the V1 projects they were working on. If your entrepreneurial like myself, you might prefer the Facebook culture.
Fourth, Google tried to match me up with a team before my start date. Facebook matches employees with teams after a 6-week bootcamp. I liked the latter approach, because I could really get to know teams before I joined.
I joined Facebook last week, and my first impressions have backed up my intuition.