> For a realistic-sized problem, if you write solutions in C and Python with the same amount of effort from equally skilled programmers, the Python version will almost certainly be faster, because they'll have had a lot more time available to spend prototyping and picking good algorithms rather than debugging undefined behaviour because they used the wrong combination of integer bit lengths.
I think this is more nuanced than that. Competitive programming actually gives fairly good insight here, because skilled programmers are placed under time constraints and obviously care about performance.
What you see, usually, is that programs that don't need maximum performance are often written in Python, which allows people to quickly write code that needs less debugging. But double the allotted time and the C programmer finally has their code finished and free of bugs, and they're beating the pants off of your Python code right out of the gate. You try and come up with clever ways to avoid copies and drive down the Big-O, but the C programmer comes up with the same thing just a bit behind you and leads most of the time because they get a free 10x speedup just because of the language they're using.
It's not surprising that the highest levels of competitive programming are dominated by C (and to a greater extent, C++) programmers, with Python use extremely rare, almost always reserved for rare, complicated algorithms that happen to bring a significant big-O improvement that justify the use of Python to write them.