GoToWebinar is one of the major webinar softwares in the space in terms of market share. Originally founded in 2006, it still maintains a lot of the same design elements that were used over 10 years ago.
GoToWebinar provides a webcast version of their software, but the majority of events are run with the standard downloaded version.
Zoom was founded in 2011, and they've had incredible growth since launching. Zoom is mainly known as a meetings platform, not a webinar platform. It's reliable, stable, and has great stream quality, and these features work really well for meetings. However, as a webinar platform, it's lacking quite a few marketing features, deep integrations, and it also requires a download for all attendees.