If it was the GSP of a year ago, I'd pick Serra again. But his improvement since then has been amazing. I make Serra a live underdog though, because he'll compete. Plus, people forget that Serra competed VERY well against BJ Penn years ago. But I'll still take GSP.
BTW, I competed in my very 1st cage match a couple of weeks ago. ZERO ground training. No wrestling or BJJ EVER trained. No MMA gym. I got smoked, but avoided a guillotine (was gurgling) and reversed the guy, from the bottom mount position. He was a very established amateur fighter, who said he's going pro soon. I lost badly, but was happy that I gave it 100% (never turned over from the bottom and didn't submit from a tough position). Unbelievable experience.