If you're on Python and you for some weird reason absolutely have to use RSA, make sure to use RSA-OAEP and the pyca/cryptography library: https://cryptography.io/en/latest/hazmat/primitives/asymmetr...

sybrenstuvel/python-rsa/ is PKCSv1.5 which like lvh said, is not secure.

RSA is fundamentally less secure than Diffie-Hellman as it lacks forward secrecy. So even a perfect implementation is still less secure.