The CFI experience will really pay off when you upgrade to CA at an airline. You will already have experience as a PIC in a professional environement where you had to balance safety, on-time performance, Mx, Wx, Management pressure, and customer demands all while supervising another pilot.

In their first 1000+ hours, new pilots are still getting used to the aviation environment...there are things that you have to think about now that will become second nature 1000 hours from now. More comfort in the aviation environemnt will help you with airline sim training (but not groundshool, that's just academics).