Q:

Are supersets an effective way to gain size? 

Following is my Chest and Back split:

3 supersets of flat barbell bench press/flat dumbbell flyes (10-12
  Reps)
3 supersets of incline barbell bench press/decline dumbbell flyes (7-9
  Reps)
3 supersets of decline barbell bench press/incline dumbbell flyes (6-8
  Reps)
Then I follow this up with 9 sets of a Back workout (No supersets
  involved). 

Personally, I love this routine because I get a good chest pump and my triceps and shoulders engage a lot as well (Probably exhausted to failure after the last set of the chest workout).  However, my question is, would supersets be efficient as compared to doing all these exercises in isolation when the underlying goal is to gain size? 

A:

Considering your goals to increase size, supersets are not as efficient in comparison to doing these exercises in isolation.  During the execution of a superset, each previous set makes significant in-roads into your ability to perform the next set in sequence as optimally as without.  Given all other things being equal, the increase in the cross-sectional size of a muscle is proportional to the increase in its ability to resist more weight.  If you were to split the proposed superset exercises across multiple days, your ability to lift more weight on all the exercises would increase significantly, allowing for greater levels of hypertrophy.