userEvent is considered to be a more reliable and secure way of triggering events in the browser because user events are events that are triggered by a user's interaction with the webpage and reflect the actual user behavior on the page. However, fireEvent is a means of programmatically activating an event (dispatching DOM events) in the browser, which can be less dependable.

Reference: https://testing-library.com/docs/user-event/intro/#difference-to-fireevent