I voted 665 cause I havent shot the 660.
I bought a whole lot of Mag Blends last year and when I got a new toy (remington 870 SPS) for christmas, I decided to give the more open choke a try and went with the 665.
I shot it against a PG and IC and they were all very comparable but I was very pleased with the JH 665 with the Mag Blends.