You’re getting ahead of yourself here.
There are several distinct steps in both the K-1/CR-1 processes. They both start with a petition and end with an interview.
Some of the processing times you’re seeing might be for the petition approval alone.
Since they both currently take around two years overall, easily the best choice is the CR-1, as there is no delay with the green card.
US immigration is not cheap, fast, or easy. I suggest the USC petitioner joins the convo here.