it’s no one’s business why people choose to abort.

This. The only answer to "why" is "fuck off", and for so many reasons. It'd suck to agonize over the decision, and once it's made to then be second-guessed by some rando.

I mean more like "is a life of suffering worth living and would a parent want that for their kid" rather than the ethics of abortion

In my country it is legal to abort just because you don't want the kid, but illegal to abort for a certain specific reason (the parents not wanting a girl). This is because people might abort daughters if they are poor and think that girls are less likely to get jobs.

I feel that the Down's Syndrome case is similar. There are people with Down's Syndrome who lead happy lives, and genetically 'normal' people who lead miserable lives. So of course a mother has the right to abort a foetus. But I fear that if we normalise aborting children on genetic grounds, that could lead to eugenics.