I have a i9 mbp bought a few months ago.. don't. Get the i5 or i7. The i9 is expensive, gets impressively hot quickly under load, and makes the keyboard too hot to use and makes a fair bit of noise.

Whatever the fraction of performance the i5/i7 is, anything that's cooler and quieter is worth it and you don't likely notice the performance difference anyways.

Numerous things cause the fan to run flat out, for example crashplan.