The Remote Engine on the marketplace is maintained by Talend. It allows you to deploy it quickly using an existing AMI and/or a Cloudformation. Meaning, you don't have to download and build a new image yourself, which can speed your Talend adoption.
But if you need to customize, the OS / Java or including some scripts or other binaries within the image. It might be preferable to create an image by yourself.
In the end, it's really up to what you want to do and your use cases. But the AWS marketplace is about speed where using a downloaded RE will give you more flexibility
