From the side by side, it looks like they got the face more or less as it is in the bust. There’s only two real changes I see, which is the coloring and the hair. The hair on the statue is… well it’s a statue, so it kinda has to be these large curls by default. Translate that into an actual haircut, and suddenly Nero’s bowl-cut style looks a LOT worse. Ditto the beard, except, without color contrast, you can almost go without noticing it on the statue. Now there’s no avoiding it. No one escapes the beard.
So, yeah, basically he looks a lot worse because the fact that the original paint wore off the bust and the limitations of sculpting hair were helping hide that he has a bowl cut held on with a chinstrap.
