Zoom’s client blows away anything that I’ve seen from anyone else -by a significant margin.
When you can have 30 active video thumbnails on a single screen, with very little latency, on a humbly-specced machine, and the fan doesn’t even kick in, you have some impressive work.
They may have some good video-compression stuff going on. I haven't bothered to set up a network sniffer to see what is going on, but I suspect that it's a PtP vid connection.
This is because I will occasionally see only one thumbnail bork, and also the thumbnails are constantly switching places to match my screen (which I find maddening).
I think that it was Skype that had the "lowest common denominator" problem, where just one bad connection would bork the whole session. It seems that in Zoom, a single (or multiple) bad connection won't mess up the whole call.
Also, the quality doesn't seem to degrade as more people are added.
I have in the last weeks probably seen most of the tools out there and used a lot. As said in another comment my SO has to use multiple tools. So Zoom won from a usability and feature perspective for non technical users.