Hello,
This is a question I see a lot on other forums regarding flight simulators, but X-Plane is a different beast compared to triple AAA games you see, the custom built rendering engine X-Plane 11 runs on is the open source OpenGL API, but you might already know this, anyway as of now X-Plane 11 is entirely still dependent on single thread, even though some aspects of the engine now support multi-core and most likely have since X-Plane 10.51, but having fewer cores and a faster IPC would make your X-Plane experience much more smoother, do not expect to get 60FPS everywhere, the openGL engine is already nearly pushed to the limit with it constantly calculating the flight dynamics and other things in the background so therefore it just cannot do it, but there is a very high chance when X-Plane 11 eventually transitions to Vulkan you will be able to achieve higher frame-rates, and yield and even more smoother experience maybe to the level of Prepar3D, but that all depends on your hardware configuration, but anyway back to your question, you would be much better off with an i5 or preferably an i7 also do try to get a K version, as overclocking it will also help with the performance as X-Plane loves higher clocked cores more than multiple cores.
I hope I helped you. :)