I usually buy chunky-without-salt (from Trader Joes). Kyle prefers his pb with salt, so when I've baked these cookies I've found that I like them best when I use a 1:1 mixture of salty and not-salty.

I'd imagine that creamy pb would make smoother, flatter cookies, but I haven't tried it. The recipe also works very well with almond butter -- I put an almond on top of each one instead of flattening them with a fork, and it makes a wonderful kosher-for-Passover macaroon.