Based on fruits from our own tree and those from some friends, my wife and I prefer the abiu (we have a Z-1 cultivar) to star apples, though there is some similarity in taste. Sapodilla is quite a bit different, with a strong brown sugar taste compared to the milder vanilla/pear/caramel taste of the abiu. An abiu, picked the same day and chilled in the refrigerator, makes for a beautiful, wonderful dessert.
Chris