One is built for carts.
The other for newsletters.

What the comparison usually misses

Klaviyo's advantage is conditional

Nearly every Klaviyo vs Mailchimp article concludes that Klaviyo wins on automation. That is true, and it is true because of one assumption: that your customers browse products, add them to a cart, and sometimes leave. Remove that assumption and the advantage evaporates. A yoga studio has no abandoned carts. A florist has no browse-abandonment sequence. You are then paying premium per-contact rates for machinery that has nothing to run on.

Mailchimp's advantage is that it asks less of you

If your realistic ambition is a decent-looking email once or twice a month, Mailchimp gets you there faster and cheaper. The trade is that it will not do anything clever with your sales data, because for the most part it cannot see your sales data.

Both report on the wrong number

Open rates stopped being trustworthy when mail clients began pre-fetching images on the recipient's behalf. Yet opens and clicks are still the headline metric on both dashboards, which means a campaign can look like a success and produce no customers. For a business with a register, the only number that settles the argument is how much money came through it.

There is a third option

Cherub connects to Square, Shopify or Mindbody, watches what actually sold, and writes the campaign when there is a reason to. Promo codes go into your point-of-sale system, so when someone redeems one the revenue is matched back to the campaign that sent it. You approve before anything goes out, and nothing goes out on a week when there is nothing worth saying.