1. When the Opponents hold an odd number of cards in a suit, statistically they will be divided as evenly as possible more often than not.
   

   Opponents hold	Distribution Statistics		Opponents hold	Distribution Statistics
   5 cards	68%   :   3-2 28%   :   4-1   4%   :   5-0		3 cards	78%   :   2-1 22%   :   3-0

   
   
2. When the Opponents hold an even number of cards in a suit, statistically they will be divided unevenly more often than not
   

   Opponents hold	Distribution Statistics		Opponents hold	Distribution Statistics
   6 cards	35%   :   3-3 48%   :   4-2 17%   :   5-1 or 6-0		4 cards	41%   :   2-2 50%   :   3-1   9%   :   4-0

It follows that if you have an 8-card trump fit, Opponents' 5 trump cards will most often be divided 3-2. A very favourable situation.

But if you hold 7 trumps only the Opponent's 6 trumps are likely to break 4-2 or worse.   If your trump holding is split 4-3 you may be in danger of losing control during the later stage of the game. (A 5-2 split is less disadvantageous.)