does pyodbc have any design advantages over pypyodbc?

Potential advantages of pyodbc over pypyodbc by being written in C would be:

• speed - see the pypyodbc wiki comparison
• more conservative memory usage

Potential advantages of pypyodbc over pyodbc by written in Python would be:

• Less likely to contain C pointer issues
• Slightly less likely to contain memory allocation issues
• Simpler to maintain; a higher-level language means less lines of code
• Much much easier to install without compilation issues which require a separate build for separate versions of Python, platform etc

Advantages of maturity:

• Fewer bugs
• More comprehensive coverage of features
• Better handling of corner-cases

The maturity thing is largely dependent on pyodbc not being buggy. In my past experience (around 2016) that was not true and it had had a fair number of memory leak bugs etc. But since then pyodbc has been improved significantly and is now properly maintained.

The author's claim is that pypyodbc is a reimplementation of the pyodbc code in Python, and that would mean that the feature coverage should be equivalent. There may be some corner cases that have been less tried in the newer code though.

Disclaimer: I haven't yet tried pypyodbc