CC0 is much more thorough than the Unlicense, was written by actual lawyers, and has a fallback to a maximally-permissive license in jurisdictions where willing

CC0 is much more thorough than the Unlicense, was written by actual lawyers, and has a fallback to a maximally-permissive license in jurisdictions where willing relinquishment of copyrights into the public domain doesn't exist. Unlicense doesn't have any of these properties so it really should be strongly avoided when choosing a license for a project -- there's no benefit to using it over CC0 and several potential (though admittedly theoretical) downsides. The Unlicense website also incorrectly states that "CC0 is not intended for software" -- while the other CC licensed aren't good choices for software, CC0 most definitely is intended to be used for software as much as any other copyrightable work.