Thanks for posting this list! As it happens I am working on organizing a conference in the coming months and I've been comparing a few similar platforms but there are several on your list and in the comments that I didn't know about.
If anyone has attended a conference recently using one of these platforms I'd love to hear how it went.
We actually are working on a broadcast feature so that you can have speakers talk across rooms. And people can still interact with each other. If you will be interested in trying it out, let me know.
If anyone has attended a conference recently using one of these platforms I'd love to hear how it went.