Is there a significant difference between having these types of signs?
ANSI is a private organization that creates voluntary standards, while OSHA is a regulatory government body that has the power to write ANSI standards into occupational law.
ANSI - https://www.ansi.org/about_ansi/introduction/introduction
OSHA - https://www.osha.gov/about.html
OSHA and ANSI co-operation https://www.osha.gov/laws-regs/mou/1991-05-21