You make a good point in saying their conversion rates are likely higher just as a matter of them being right.

I think Hitchens and Dawkins provide a much needed antithetical punch in the nose of religion's thesis.

For deconverts from Christianity (like myself), I'd credit them with being something like an atheist pastor during the strange existential/nihilistic void that many feel after losing faith.

I suppose I did read them to feel more secure in my worldview and confirm my beliefs (or rather doubts)... but it felt more like a much-needed antidote to the long-standing effects religion's poison.