If you make your scraper well, and it counterfeits being a real user believably, you end up with a solution that can be tweaked as needed to handle whatever traps people put in to try to defeat your scrapers.

If you make your api client well, you don't have the problems of a scraper - but if the api owner decides to change rules for api and you can't do what your business is based on being able to do (think of api owner as Twitter) then you need to make a scraper.