This discussion is specifically about facebook vs. G+; not a random site with 1,000 users. We know that both sites have achieved significant user-base. We also

This discussion is specifically about facebook vs. G+; not a random site with 1,000 users. We know that both sites have achieved significant user-base. We also know that one of those sites has crazy engagement and that it's had crazy engagement for a long time. That site is facebook. We know that the other site has 40+M members but publishes no engagement metrics and when pushed, avoids questions about engagement. It is not a stretch to assume from this that their engagement is not optimal. It is safe to say that facebook wins the engagement war. The common counterargument is "but G+ only launched few months ago." To this, I counter that few months into facebook's launch, their engagement was very high. The next common argument is that "but G+ got 40M+ members in few months." To this I say that the 40+M number says very little about G+ and says much about the Google search engine. As an example, I'd argue Google can launch a fictitious service and get tens of millions of signups for it by linking to it from google.com.