The “Language Committee” of the early Zionist period (precursor to the Academy of Hebrew Language) debated this topic at length, along with teachers of the Hebrew schools. The majority opinion was that the Sephardi pronunciation was preferable, for several reasons:
- It was closer to the pronunciation in antiquity than the Ashkenazi pronunciation
- It was the existing pronunciation among Hebrew-speakers in Jerusalem’s markets
- There was much greater consistency in pronunciation among the various Sephardi communities than in the Ashkenazi ones
- The Sephardi pronunciation was considered “more aesthetically pleasing”
- The Zionist pioneers sought to distance themselves from the shtetls (small Orthodox Jewish communities in eastern Europe) in speech as well as lifestyle.
However, as Yishai Barr points out, what happened in reality is that the decision to adopt the Sephardi pronunciation was constrained by the abilities of the Ashkenazi Zionists to do so. As Shlomo Geutein, head of Hebrew instruction under British Mandatory rule, aptly put it:
המבטא המקובל ביישוב הוא ספרדי לפי הרצון ואשכנזי לפי היכולת. הוא מנסה להיות ספרדי באמצעות ההגיים הנמצאים באשכנזית
(“The conventional accent [sic] in the Jewish community [in Palestine] is Sephardi by choice, but Ashkenazi by ability. It tries to be Sephardi through the Ashkenazi manner of speaking.”)
So this would explain why certain sounds like that of ayin for example lost their original pronunciations? E.g. ayin and aleph now sound alike in modern Hebrew.