As a use of both SES, and MailChimp (as well as SendGrid for transactional) for https://Clara.io I find no difference between SES and MailChimp regarding delivery. It would be cool to see an objective study here. Otherwise it seems like FUD.
I don't use either, but I have to deal with spammers from both. The difference is that Mailchimp has a zero tolerance policy to abuse, whereas SES doesn't.