The big win for me, and the reason I use Netlify, is that it gives you atomic deploys without any effort. `aws s3 sync` works fine in most cases, but its not atomic, so if you want to make sure what you're deploying is going to work for 100% of users all the time you end up having to build something more complex - at the simplest that involves adding a hash to all your files, making sure they're deployed, and only then pushing index.html (and any other entrypoints).

With Netlify I can just hook it up to Github and they'll handle running any build scripts, and then smoothly flip from the previous version to the new one in single action.