What are the scenarios which the one (e-Newsletter) or the other (MailChimp Integration) plugin is recommended for? In other words, what are the target configurations/usages for each one? Is there one for professional entry level and the other one for advanced usage? Let's not talk about money, let's talk about professional usage.
By the way, the MailChimp Integration plugin page says: "we use it ourselves". What is WPMU DEV's short and long terms strategy: stay with MailChimp or switch to e-Newsletter plugin?