Dear Rabbi Simon,
Our Shul is Modern Orthodox. We are looking at acquiring a new Sefer Torah. My limited understanding is that we have a choice between Ari or Beit Yosef. Which would you recommend for our kehillah? What essentially is the difference?
Go for the Beit Yosef (see Bereshit 41:55). This is the “font” prescribed by Rav Yosef Karo in the Shulkhan Arukh and has been standard throughout the Ashkenazic world for centuries (even though Rav Yosef Karo of course was Sephardi).
The style of the Ari incorporates some aspects of the earlier, medieval script known as Vellish. It has become popular with Hassidim and many Sephardim. Chabad go their own way and use a variation of the Ari script.
The difference between Beit Yosef and Ari is in the shape of 5 or 6 letters. BTW it is doubtful if the Ari even intended his changes to be used in siferei torah. It may be that he only advocated for the change in tefillin specifically. In any case, my recommendation for a shul comprised predominantly of South African expats [even if it is not Kesher] is to go for Beit Yosef.
Rabbi Rashi Simon