Zoom is the most most fantastic software I've used for client-contractor meetings. In those cases, the clients or sub-contractors or other stakeholders will simply not use something that is hard to install and start up, or gets blocked by corporate security policies.

Zoom has always "just worked" no matter how non-computer savvy the other side was. I still use it for all kinds of personal things. I strongly, strongly, strongly recommend it.

It also has good "draw-on-someone-elses-screen" functionality, not sure how many other softwares (Skype, Slack, etc) have that. I think it's very powerful and underutilized.

Depends on how many participants. It's not uncommon for us to have 50+ attendees at some larger company/engineering meetings. Zoom seems to handle that bandwidth admirably. I've used Slack for smaller calls without incident.