You know what's kind of strange about this fruit, from my perspective? (And frustrating too.) From what I can tell, the white sapote is basically a minor fruit -- Julia Morton doesn't give any great shakes to it, you don't see fanatics discussing it like mangoes, it's not shipped, etc. But, it seems to have a real truck-load of cultivars, which substantial variation between them; but at the same time, it's not important enough for fruit nurseries to really go into much detail about it. Not only do most of them not offer much information about what cultivars they have, but most of them seem to have different varieties, and none of them are the ones that people are listing here as superior . . .
For me, it's tricky -- I probably have one shot at getting these to Thailand, and so I need to choose good varieties, that are able to pollinate each other. It's a bit of a crap-shoot; if I had to do the same thing with apples, there are many, many types I just don't care for, and a few that I love.