I've got a .660 as well but liked the patterns of the .670 a little better. I like a little more open pattern myself.
I like the option of going really long if I need to; I'm getting close to a 80%~90% pellet count inside a 10" circle at 40 yards. But, my pattern isn't much larger than a softball at 20yds~25yds. Not much room for error if one sneaks up on me.
