The Kappa may sound better but if you plan to crank it at times the Marine would probably be better. I had an all Kappa system in my car at one point, they sounded great but when my daughter began to drive the car and she thought it more important to be heard before seen the speakers were damaged. It wasn't the speakers fault, the Kappas are not efficient and not designed to be used in an SPL contest. I had my Kappa's amped which is another consideration, if you aren't going to run an amp the Kappa's are off the table. Seeing the Marine are designed for the application it is probably your best choice.