Even with higher speeds, runtime may fluctuate a lot. In order to compare performances, you need several trials.
Naturally I did a few measurements. Python scripts behaved the same way. The single-core and multi-core scripts showed approximately the same search time, although the multi-core speed was much higher.
In this case, remains the question whether the program stops running immediately or not when one of the threads finds the solution. We need to ask the developper