N1 is louder, and everyone has it or a knockoff of it, and i think its kinda geared more towards FI exhaust but im not sure. The ws2 isnt as loud and is just a simplier muffler.
ws2
http://www.youtube.com/watch?v=qDsBE...elated&search=
n1
http://www.youtube.com/watch?v=wmuZu...elated&search=