Who each tool is really for
EngageBay
EngageBay positions itself as an all-in-one platform for small businesses, covering marketing, sales and service in one product. The appeal is shape rather than scale: you get the same categories a large platform offers, in a lighter package aimed at teams without a dedicated operations function. It suits businesses that want email marketing and a pipeline in one place and would rather not run two vendors to get there.
HubSpot
HubSpot positions itself as a full customer platform, and it is genuinely large: deep marketing tooling, a substantial application marketplace, a wide partner network and a great deal of published education. It suits organisations whose growth plan depends on content and lifecycle marketing at some scale, and who have or will hire someone to run it properly.