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.
With Aweber however, this is not that easy to do. With Aweber, each and every one of your subscribers is tagged with a message number which indicates which followup emails they have received already. To prevent a subscriber from receiving a specific followup email, you must set the subscriber’s message number to be higher than the email sequence number.
Think about implementing referral links to incentivize your subscribers to spread awareness about your brand, too. Referral links allow your current customers to promote trackable links for your business. In exchange for sending new paying customers your way, you can give them incentives like discounts, coupons, vouchers, cash, prizes or redeemable points.