The number of physical cores a CPU has can certainly impact its performance, but it isn’t the only factor to consider when choosing a CPU. Factors like instruction per cycle and the cache present also factor into how a CPU performs under stress.
Of course, there are also many different applications that approach things differently in how they utilize CPUs. Those in pro audio might favor stronger single-core performance, while those working in image processing might prefer multi-threaded speed. So while the core count is important, it really is dependent on your use case.