If you are looking for scholars that will help you with your ultimate interest (medieval Islam and Christianity), I would go with Yale over Princeton. Yale has Denys Turner and John Hare who respectively cover the bases of the Dominican and Franciscan theological traditions. Indeed, Turner is an accomplished scholar on Aquinas, who as you know, was one of the first theologians to really engage with the Arab commentators. Anyway, just my two cents. Fordham is great, but it might not look as good for PHD apps.