We might be tempted to compare the functionalities of IntegrationHub & Exalate, focusing on one particular Integration scenario /need. However, it would be better to look first from a broader perspective and acknowledge that the Integration scenarios can be vastly different and ServiceNow IntegrationHub & Exalate are targeting different sorts of organization & needs.
IntegrationHub is mostly used by the enterprises that use ServiceNow as the main platform to manage IT services & intend to take the IT automation to the next level. For such a purpose, IntegrationHub (together with flow-designer and the spokes for various systems) provides an excellent foundation. And if an organization doesn't choose IntegrationHub, then the reason would likely be strategic e.g. a different platform is chosen to do the IT service automation & orchestration.
Exalate is an excellent solution for organizations with teams working on different platforms e.g. ServiceNow and Jira, that want to streamline the corporation between the teams by synchronizing their tickets. For this purpose, Exalate is a good candidate due to its flexibility, reliability & autonomy. In other words, if someone is seeking to sync incident/change/problem tickets with Jira issues/projects/stories, Exalate is a good solution.