Advantages of fast pace
-can speed up offense
-score more points
-might be able to pull away in games or keep up with better ones
Disadvantages of fast pace
-lose stamina quicker
-may cause more turnovers if sufficient HA/PA and stamina isn't there
-takes low percentage shots
Advantages of slow pace
-slow game down
-retain stamina longer
-opponent scores less
-can help you stay close to a better team
-looks for higher percentage shots
Disadvantages of slow pace
-might wait too long in the shot clock, forcing a bad shot
-teams that aren't far behind you (in terms of player quality) might be able to keep up
-scores less points
These are all the reasons I can come up with.