After about half an hour of testing, I think I prefer the 660s over the 660s2.
I got my 660s for $300. These I obviously paid full price.
They are a fun headphone and I like the changes, but overall I prefer the 660s and they'll still be my daily go-to. The 660s's sound like you're on the front of the stage, and the 660s2's sound like you're in the middle of the stage. It sounds less wide, and overall sounds v-shaped right out of the box.