One of the things I have always appreciated about Ehrman is how careful he is to present the evidence accurately and to deal with counter argument fairly. I have argued with many internet apologists using Ehrman as my primary reference and I don't think that I have ever been caught short by arguments or evidence that I couldn't have reasonably anticipated after reading Ehrman. Even if I didn't agree with Ehrman's conclusion, I always felt that I had a clear picture of the evidence upon which it was based and the counter-arguments that might be offered against it.
According to Carrier, Did Jesus Exists? consistently misstates the evidence and fails to inform the reader of the diversity of scholarly opinion on the issues it addresses. I don't have the expertise or knowledge to critique Carrier, but I can say that I have always found him reliable in the past and that no internet apologist has ever managed to trip me up when I relied on Carrier either.
Update: Carrier does address one point that I covered in an earlier post, which is the problem with the "nobody would/could have invented it" argument. Not surprisingly, he does it better.
[T]here is a logical fail here as well, since he bases his conclusion that no Jews would develop a belief in a dying messiah on the premise that no Jews had a belief in a dying messiah, which apart from being a circular argument (all novel beliefs start somewhere; you can’t argue that x would not arise because x hasn’t arisen), and apart from the fact that the inference is refuted by the fact that Jews later did develop such a belief (independently of Christianity, as I also demonstrate in the preceding link) so clearly there was no ideological barrier to doing so, but besides all that, his premise requires knowing what all Jews, of all sects, everywhere, believed or imagined, which knowledge Ehrman doesn’t have (not even close: see my discussion of what I and other scholars have said about such preposterous claims to omniscience in Proving History, pp. 129-34). He even knows his own inference is illogical, because he makes the exact same argument I just did (on p. 193): “how would we know this about ‘every’ early Christian, unless all of them left us writings and told us everything they knew and did?”* Substitute “Jew” for “Christian” and Ehrman just refuted himself.* In the quoted passage, Ehrman is addressing Rene Salm's argument that we can infer the non-existence of Nazareth from the fact that early Christians didn't bother to look for it and seemed not to know where it was.