There’s a big difference between the Trump and Biden cases. Trump violated the law by possessing classified papers and attempting to cover up his actions. The former president is facing a serious investigation because he knowingly held sensitive information and actively worked to keep it from the archives. Biden did neither of those things, thus GOP claims of Biden's hypocrisy are unfounded.
The only important difference between the two cases is that Biden was vice president when he took the documents to his private office, and vice presidents don't have the same declassification powers as presidents. It will be interesting to see whether the DOJ sends teams to raid Biden's residences as they did with Trump, or if there continues to be a double standard.