Likely not that much slower. I rather have slightly slower code that is easy to develop & maintain, than code that is fast but hard to read, hard to maintain and easy to introduce bugs in to.
I write a lot of C++, and nothing about a standard algorithm loop is hard to read or maintain. For the Python or C++ guru both are trivial to work with.
If I were doing fancy conditional transforms on maps with non-trivial modifications (ie, string manipulation) I'd almost always try to use Python first, though.
