From a brilliant discussion at the Notorious R.O.B. – (bolding mine)

While the study cites C21 as the most well known(n) brand, I will argue that it’s the most well know(n) name in real estate. But being a well known name does not make a brand. A brand is something different. Its backed by specific promises it keeps, trusts it forms that creates an identity that distinguishes it from others.

I would argue that C21 has not built that cache of brand value in the consumer world, it has hardly done it inside real estate.

But I do agree its the most recognized name in real estate. But ask any of the respondents of that survey to tell you what makes C21 different from ERA or Remax or anything and they would be hard pressed.