We are working on Arabic Natural Language Processing project, we have limited our choices to either write the code in Python or C++ (and Boost library). We are thinking of these points:

Python

Slower than C++ (There is ongoing work to make Python faster)
Better UTF8 support
Faster in writing tests and trying different algorithms

C++

Faster than Python
Familiar code, every programmer knows C or C-like code


After the project is done, it should be not very hard to port the project to another programming languages.
What do you think is better and suitable for the project?
Familiar code, every programmer knows C or C-like code

Many devs are familiar with C or C-like code, it doesn't make them C++ compliant.
Unexperienced C++ devs can do a lot of harm to such a complex project and you would have to take extra care.
I can't speak for python but I heard it's more beginner-friendly.
I'd say, once again, you should go for the language you (as a team) know best.
NLP project, python or C++