The verdict
If your team already uses Zoom every day and your audience knows it, pick Zoom Webinars. Your hosts already know the interface, and you can add the broadcast side without a second vendor.
If you do not use Zoom, or you need payments for paid events and certifications, pick GoTo Webinar. It is also the natural pick if you already use other GoTo products.
This truly depends on your stack. For a small B2B team starting fresh, I'd compare both with a browser-based tool such as Livestorm before you commit, since GoTo's pricing is not clearly listed and Zoom's cost depends on your tier and host count.