Is speed or accuracy more important in pitching?
Accuracy hands down. A major league hitter can turn on a 95+ mph fastball easily if it's not placed in a good location. A pitcher like Greg Maddox who averaged an 88 mph fastball but had pinpoint location is a Hall of Famer. Placement and off speed pitches is what makes great pitchers.
Mariano Rivera who was probably the greatest closer of all time pitched in the mid-90's but his cut fast ball is what got the batter.