Over the last two years, I've been using Zoom simultaneous interpretation as an interpreter, as a meeting host (remote and on-site tech support) and as a conference rental sound and video engineer extensively, in all possible configurations, including hybrid events with interpreters working remotely from their home office as well as on-site using hardware interpreter consoles.
Since Webex interpretation is a new thing for now, there's not enough real-life experience to make conclusions regarding its stability and potential issues.
Here's the link
to the official Webex support page on simultaneous interpretation that lists several known issues and limitations.
The way Webex simultaneous interpretation is designed suggests that hybrid events combining online and offline participants and interpreters are also possible with Webex on par with Zoom.
Here's my subjective comparison of Zoom and Webex simultaneous interpretation features.