The United States Patent and Trademark Office (USPTO) provides invalidity tools via inter partes review (IPR) and post-grant review (PGR), but which route is better? … PGRs are estimated to cost more because of their broader discovery rules. If cost is a major factor, IPRs are a less-expensive option due to restricted allowance of discovery, the most expensive aspect of patent litigation… If the invalidating arguments or art are not strong, an IPR may be a better option due to its lower threshold for institution. The same prior art arguments that failed in a petition for a PGR may have succeeded in an IPR petition due to the lower standard.