I disagree. Most people think GSP has better striking then BJ because what stands out in BJs career are his submissions but his striking is top notch. I really don't see him KOing BJ especially since he has never KOed anyone in a pro fight.
BJ isn't going to be the first one. BJ on the other hand has KOed Caol Uno and went toe to toe with Gomi. Granted Gomi is much lighter then GSP but for sure in a standup only fight Gomi>GSP.
I think GSP has a strength advantage but I don't think he can outstrike BJ. I also think GSP's wrestling is better then Penn's, but Penn wins the striking and submission matches.