The verdict
For a small B2B team, I'd pick Brevo. It gives you a simple CRM and a text channel next to email, and one automation can hand a lead to sales. Kit has no deal pipelines or account-based features, so you meet its ceiling quickly in a sales-led business.
If you write a newsletter, sell a course or digital products, or run a paid newsletter, I'd pick Kit. Its tags and visual automations are easy to follow, and the commerce tools remove the need for a separate checkout.
Both grow in cost as you grow, so model your list a year ahead. Kit offers free migrations according to its site, which lowers the cost of trying it.