The verdict
If your team is standardised on Zoom and you need large broadcasts, pick Zoom Webinars. Your hosts already know the interface, and there is no second tool to learn. If webinars and events are a core channel and you want on-demand hubs, learning content, hybrid and in-person events on one platform, pick BigMarker.
For a small team that runs the odd webinar and already pays for Zoom, I would start with Zoom Webinars. For a team with a real events programme, compare BigMarker. Check that the tier you are quoted holds the features you need. Capacity and event features depend on the Zoom tier, and BigMarker keeps API access and single sign-on on enterprise tiers.