The verdict
For online-only webinars and training, with CRM sync and attendance reports, pick GoTo Webinar. It does the job without the weight of a full event platform.
For hybrid conferences with several tracks, a mobile app, sponsors and a need to report across in-person and online guests, pick Webex Events. This is strongest when your company already runs on Webex or Cisco.
This truly depends on the event. If you are a small B2B team running mostly webinars, I'd compare both against a self-serve tool first, because neither is quick to buy. If you must choose between these two, match the tool to the format and ask each for a written quote.