Is there a difference between using CDN for files on s3 and holding files on the machine?

If the files are hosted together on the server and not on the outside, does this have an impact (better or worse) on cdn (cloudfront) ?

I want to move the files to S3 in order to set up CDN (separate) as well. Is it worth it or doesn’t it make complete sense to do it (VPS 50GB (20gb free)) ?