Microsoft, Yahoo, and Google are indistinguishable with regards to their policies in this matter. A hypothetical startup which did not have or particularly want a presence in the Chinese market could differentiate on this.

Granted, they'd have to be pretty adroit about it, but it is a compelling PR story since it makes Google look like the giant, not-particularly-moral, profit-focused advertising firm that they are instead of the two dudes in a dormroom that they pretend to be (and probably actually seem themselves as).