The amount of work is on the server side, but they are forks of the same code. The sharing side is not as complex. Plex has hit an impass on remaining solvent as a business. Emby is even in a better situation than Plex is and quite frankly, I don’t see a reason to use them when Jellyfin is an option.
I have always believed that the majority of the world’s problems stem from almost all of the world’s countries rely on a private bank to print and regulate their money. Those banks aren’t capitalistic, but I bet the people behind them are the richest in the world.