The largest factor, which no one else seems to have mentioned, is that when you are talking above ground pool, you are usually talking Intex. The tiny cartridge filters that come with their pools are just terrible. No one with an Intex pool should consider using that filter. The most affordable upgrade is an Intex sand filter, which will actually filter the water. There are plenty of other filter options, but all of the other ones worth considering are significantly more expensive than an Intex sand filter, leaving it as the only practical choice for people on a tight budget.
If your budget is larger it is a whole different story.