I have used both, and I agree with your analysis. The great thing about MailChimp is that it lets you see the email in different clients. That is really the hardest thing about sending emails. However, you can use that service without doing everything else through MailChimp. Also, once you get the hang of it and develop templates, it no longer is much of an issue.
Follow-Up Series (Autoresponders): In addition to one-time email blasts (called Broadcasts), AWeber allows you to create chains of autoresponders (campaigns). An example would be a welcome email which is sent to each new subscriber who signs up, then a series of weekly “How To” emails explaining the various applications of your product. You can set the interval between these messages to anywhere between 0 and 999 days. You can also start subscribers at different points in the cycle if you wish (so for instance, if you had a separate signup form for advanced flying widget users, you could start them on #5 of your series (“New Applications of Flying Widgets”) instead of #1 (“What is a Flying Widget?”). You can set up separate follow-up series for each list, and you can copy them between lists. You can even set it to stop sending messages once the email has been opened.
Email marketing has the highest conversion rates of any marketing channel. In fact, sixty-six percent of online consumers made a purchase after receiving an email marketing message — which is more than social and direct mail, according to the Data & Marketing Association. And transactions from email are three times more profitable than those made on social media, reports the global management consulting firm McKinsey & Company.