Should the possessive of Columbus be Columbus’ or Columbus’s?
References you could find on-line are all over the place on this. When I learned about The Rebellion of Shay in Alerican History, it was emphatically mentioned that it’s “Shays’s Rebellion”. The above-linked Wiki article calls it “Shays’ Rebellion”. Googling for it, you can find many cites both ways.
So there doesn’t seem to be a widely-agreed-to rule for how to make possessive a name that already ends with s.
I believe this is one of those British/American splits. American style is generally to write Columbus’ memory; British style is generally to write Columbus’s memory. Neither is inherently better than the other.
I still feel you’re better off comparing like to like. Either compare the perception of Columbus to the perceptions of Washington and Edison or compare Columbus to Washington and Edison.