«Our most prolific reviewers seem to prefer Gerrit»{{citation needed}}
Do you mean the reviewers who are most prolific right now, those who were most prolific before the Git conversion or a mix of the two? And where are the stats? I know the analytics team is working on gerrit-stats but not what the project specifications include (there's only been an email here in April), see https://www.mediawiki.org/wiki/Talk:Analytics/Reportcard.
Nemo