I know that Pypyodbc is the newer version of Pyodbc. A question before asked about the comparison between these two but I want to add Pymssql into the mix.
As of July 2021:
pyodbc is under active (though somewhat sporatic) development, and it has a couple of Microsoft employees contributing bug fixes and new features that relate to accessing SQL Server, Azure SQL, and related Microsoft products.
pypyodbc came along after pyodbc but is not "the newer version of Pyodbc", it is an alternative pure-Python implementation. It has not seen an official release since January 2017.
pymssql lost a lot of momentum and was discontinued in November 2019. Since then a couple of contributors have stepped up to keep the project going and there was even an official release in September 2020.
However, pypyodbc and pymssql still lack some features available to users of pyodbc, particularly the fast_executemany feature to improve the performance of bulk inserts. pymssql can also be difficult to configure for secure connections (e.g., as required by Azure SQL), especially on Windows clients.