Python are two popular libraries for creating Python bindings for C++ code. Both libraries have their own strengths and weaknesses, and the best choice for a particular project will depend on the specific needs of that project. 
 
pybind11 is a lightweight header-only library that is considered to be easier to use than Boost.Python. It also has a more modern C++ API and supports newer C++ features. pybind11 is also generally faster than Boost.Python, and it generates smaller binaries. 

Boost.Python is a more mature library than pybind11, and it has a wider range of features. It is also more widely used than pybind11, so there is a larger community of users to support you. However, Boost.Python is also more complex than pybind11, and it can be more difficult to learn. 
 
Here is a table summarizing the key differences between pybind11 and Boost.Python: 
 
 

Features 

PyBind11 

Boost 

Ease of use           

Easier 

More difficult 

C++ API  

More modern 

More mature 

C++ features 

Supports newer features 

Supports a wider range of features 

Performance 

Faster 

Slower 

Binary size 

smaller 

larger 

Community 

smaller 

larger 

 
In general, pybind11 is a good choice for projects that need a lightweight and easy-to-use library. Boost.Python is a good choice for projects that need a mature and feature-rich library. 
 
Here is a more detailed comparison of the two libraries: 
 
Ease of use: 
 
pybind11 is generally considered to be easier to use than Boost.Python. This is because pybind11 uses a more modern C++ API that is less verbose and more intuitive. Boost.Python, on the other hand, is a more mature library and its API is more complex. 
 
C++ API: 
 
pybind11 uses a more modern C++ API that supports newer C++ features. This means that you can use pybind11 to bind C++ code that uses newer C++ features, such as lambdas and move semantics. Boost.Python, on the other hand, uses a more mature C++ API that does not support newer C++ features. 
 
C++ features: 
 
pybind11 supports a wider range of C++ features than Boost.Python. This means that you can use pybind11 to bind C++ code that uses a wider range of features, such as templates and exceptions. Boost.Python, on the other hand, supports a more limited range of C++ features. 
 
Performance: 
 
pybind11 is generally faster than Boost.Python. This is because pybind11 generates smaller binaries that are more efficient to execute. Boost.Python, on the other hand, generates larger binaries that are less efficient to execute. 
 
Binary size: 
 
pybind11 generates smaller binaries than Boost.Python. This is because pybind11 is a header-only library and does not require any additional libraries to be linked against. Boost.Python, on the other hand, is a library that requires additional libraries to be linked against, which can increase the size of the binary. 
 
Community: 
 
pybind11 has a smaller community than Boost.Python. This means that there are fewer resources available for pybind11 users, such as documentation and tutorials. Boost.Python, on the other hand, has a larger community, which means that there are more resources available for Boost.Python users. 
 
Conclusion: 
 
The best choice for a particular project will depend on the specific needs of that project. If you need a lightweight and easy-to-use library, then pybind11 is a good choice. If you need a mature and feature-rich library, then Boost.Python is a good choice.