IGN has reviewed both fairly well. As of Sept 11, the PS3 review hasn't been released yet, but I'm sure it'll be pretty close to the XBOX review:
NHL 08 Review - Score 8.6
http://ps3.ign.com/articles/819/819015p1.html
NHL 2K8 Review - Score 8.5 (XBOX 360)
http://xbox360.ign.com/articles/819/819464p1.html