Bird's take is transparently confessional, going so far as to defend the virgin birth, that Jesus thought he was divine, and that he wasn't wrong about the kingdom's timetable. Crossley's rejoinder on all these points is right on the money, and as he notes, Bird's evangelical view makes him more or less obligated to argue this stuff. I was getting a very bad feeling for Bird in this chapter, but thankfully he gets better as the book goes on.
Jumping to the end, where Crossley and Bird give alternative accounts of Christianity's ultimate success, I think the former again shows more argumentative strength. Believers like to hold up what's theologically distinctive and appealing, but religions usually triumph for more mundane reasons, even accidentally. The west would have probably become Islamic if Charles Martel had lost the Battle of Tours in 732 (think how different the world would be today if a very minor battle had gone the other way). Sociological accounts of Christian origins may not be the most exciting things to read about, but Crossley is right that "Bird's near-complete reliance on ideas and individual influence is odd and outdated" (p 166)
I think, generally speaking, that Rosson's review is fair and well-done. And I think scholarly skepticism of the virgin birth is something evangelicals HAVE to learn to deal with. It's a leap of faith, and, in my humble opinion, that's exactly how it should be. Faith is faith precisely because it lacks scientific verification. I agree that religions do, to some extent and with many exceptions, rise to a degree of prominence based on historical factors such as economics, class warfare, colonialism. I think we can, and should, look at Marxist accounts when doing religious studies. That being said, I feel Rosson overstates the "gullibility," if you will, of the evangelical position. What is inherently wrong with the faith-based assumption that historical factors are so construed as to give Christianity the seedlings necessary to plant and grow? Obviously this is a Christianization of history. And, perhaps more obviously, such a statement draws ire from the academy at large. But, I personally don't find quite the dichotomy between theology & history as Rosson posits.