In character I can see Surfer losing more than not, maybe getting a 4/10.
Taking the fight seriously and respecting the power of Plutonian, I would expect Surfer to win 7-8/10. As he has the same abilities as Plutonian, similar intellect (Norrin was a scientist before all this) and a far longer history of creatively using the PC.
I don't see him being over-powered or out-matched in terms of versatility and Surfer has several avenues of attack that I haven't seen Plutonian defend against (genetic manipulation, mind control, astral bfr etc etc).
Also, Surfer could simply unleash more power than anyone in Plutonian's universe has ever used against him. Given that Surfer's taken on far more powerful foes and won/survived, I think it remains for Plutonian to prove he's up to the task of taking such punishment.
All in all, CISfree Surver wins, regular in-character Surfer loses more often than not.