I abandoned Mailchimp when the business model started changing, but I'll second the idea that it's better to have more control over your own web presence if you can afford it.
Free now doesn't mean free forever. Just look at how Mailchimp has already modified its fee structure, stripping down the free plan and charging more for other tiers. My personal favorite is counting unsubscribes as part of your audience so that MC could charge for them. I'd be worried that the free website would at some point begin to cost something and/or lose features that would then only be available for extra cost.
For people who truly want free, there are other alternatives.
The Mailchimp approach (charging more but bundling in all kinds of things beyond newsletter support) I've been told might actually make sense for a larger business and even be cheaper for them. But those economics don't work the same way for an indie author.