All three of those platforms have released some numbers recently, and both the usage and the growth rate of the usage seems pretty comparable. All of the following quotes are from during April:

One of them says:

> Since January, we’ve seen $SOFTWARE’s peak daily usage grow by 30x. As of this month, $SOFTWARE is hosting 3 billion minutes of video meetings and adding roughly 3 million new users every day. And as of last week, $SOFTWARE’s daily meeting participants surpassed 100 million.

Another:

> We’ve seen a new daily record of 2.7 billion meeting minutes in one day, a 200 percent increase from 900 million on March 16. [...] We’ve also seen total video calls in $SOFTWARE grow by over 1,000 percent in the month of March

And the final one:

> The maximum number of daily meeting participants, both free and paid, conducted on $SOFTWARE was approximately 10 million. In March this year, we reached more than 200 million daily meeting participants, both free and paid.

The quotes are not from the same time during April, and are not directly comparable in that sense. But if we're talking about the three options being a month apart on an exponential growth curve, it seems premature to call winners.