Serra has KO power and good BJJ, but Shields has better wrestling.
i think Serra would win by KO, because people take his standup lightly. they think the GSP win was a fluke, and while i dunno if he could do it again, he earned that win. he timed GSP perfectly, and laid him out for it, and Shields isn't even close to GSPs level standing.
im pretty sure it would be a very competitive fight, with a lot of technical grappling.
HW: Cro Cop | Barnett | Gonzaga
LHW: Rampage| Shogun
MW: KANG | Sakuraba | Spider Silva | Baroni | Akiyama
WW: Thiago Alves | GSP | Mach
LW: Gomi | BJ Penn | Aoki | Jamie Varner reppin' AZCS | DIDA
9-7 in sig/av bets