The verdict
If you run hybrid conferences and your company already uses Webex or Cisco products, pick Webex Events. One vendor for registration, delivery and reporting is the draw.
If your team is standardised on Zoom and your events are mostly online broadcasts, pick Zoom Webinars. Your hosts already know the interface.
This truly depends on your stack and the event format. Webex Events does not publish prices and may be bundled into select enterprise agreements. Zoom adds a per-host cost on top of its licence. For a small B2B team running only webinars, I'd also compare a lighter tool such as Livestorm before choosing either.