I got the PK2's last Spring. About a month later I got a set of RE2's. At first, I thought the RE2's were far inferior. They have less "body" and less low end than the PK2's. However, the more I've listened to the RE2's, the more I like them. Now I'd say it's close. They have different types of sound. If you like the "inside your head" sound and more isolation, the RE2's are good, provided you don't need heavy bass. If you don't need the isolation and prefer something closer to the sound of full-sized headphones, then the PK2's are better.
Both good and worth the money, just in different ways.