Real life closers, especialy those of recent vintage, actually have a severe disadvantage, in my opinion. Since most managers use their closers for 1 IP only, you tend to see these guys with IP/G or right around 1.0. Which means they are only good for 15 pitchers per game before fatigue sets in, and it sets in quickly. So if a batter or two reaches base, either your closer sees his performance deteriorate rapidly from fatigue, or you have to replace him.
This is a slight generalization, but low IP starters with low WHIP (Milacki, Niggeling, Northrop, Babe Adams, etc) are, in my opinion, the best closers because they never face this "in-game" fatigue problem.