Comment by junar

As Peter says, K1 is not a option for you because you're married. F2A will convert to immediate relative (either CR1 or IR1) once you become a US citizen.

CR1/IR1 is generally superior from the perspective of the immigrant spouse. However, CR1/IR1 does not allow derivatives, unlike F2A. If you have any children or stepchildren that don't have US citizenship or a green card, you will need to file a separate I-130 for them if you become a US citizen.