Najdi vs hejazi

Hello, I’ve taught myself Fusha and now I’m moving on to different dialects, and I’ve been told to learn najdi since it’s very close to MSA and it’s widely understood and useful for business (I’m 17m about to start uni and I plan on going into that field). However, I’ve noticed that hejazi is also another common dialect in Saudi Arabia, but which one should I learn? Is there an advantage in learning Najdi first and then hejazi or vice versa?

I was also just curious about the differences in those two dialects, and any explanation will help!