Ubuntu has the early lead in the https://www.osscensus.org/ census currently
under way. Ubuntu is on well over half of the computers enrolled in the survey.
Firefox is the most common open source application. If your favorite distro is
not represented or you have favorite applications that you want to see promoted
go to the above link and take the survey. It involves downloading an application
that scans your system and can take minutes or hours depending on how big and
complex your setup is. You have to sign up for a free account if you want to
participate. The only skill you need is to be able to extract the files from the
compressed archive and then cut and paste the commands given on the site into a
console window.