[Lil' Lavery]

Let's take a look at this problem from the very beginning of the match. Each alliance gets 40 balls to dispose of at their will (10+ MUST be at HP station though).
In a perfect world, all 3 robots could hit 3 pointers, and hit every 3 pointer they made (and every HP would get their ball into the robot every time). Therefore, no ball would ever end up on the field.
But this isn't a perfect world, there will be error. And seeing as you should always assume the worst when preparing strategy, we'll pretend that your alliance isnt perfect, but by some fluke you end up against 254, 71, and 233 (or some other "perfect alliance"). You will NOT be hitting 100% of your shots into the center goal, while they will. Therefore, if you cannot pick up your missed shots, a few options (and their results) appear:
a)push them into the "your" corner goal. Because the opposing alliance is hitting 100% of their shots, when their HP re-introduces the ball, it will be scored for 3 points, while the corner goal only gave you 1.
Net Result: -2 points
b)Leave them on the floor. Now we reach the point where we look at the opposing alliance's robot capabilities once again. In a "perfect alliance" all 3 robots would be able to load balls from both the HP and the ground. Therefore the opposing robots would gather the balls and shoot them for 3 points.
(In a non-perfect world, an alliance may lack the capability of loading balls, and would leave them in the exact same predicament as you for point swings per ball and how to distribute it, making this a very viable solution to leave the balls on the field in those matches)
Net Result: -3 points
c)push the balls into "their" corner goal (the one with your HPs). This will score 1 point for the opposing alliance, but give YOUR HP control of the ball, which, in the best case can result in a 3 point score for you (not counting the minimum of 1 point cost to grant the ball to your HP, and the amount of field movement time to get from your HP station to your effective firing range). But, for every shot you miss with that ball before you hit the shot, its a loss of 1 point that is not counter-acted in any way.
Net result: +2 (AT BEST)

Therefore, only one real reaction can give you ANY positive points from leaving balls on the field, and even then, not as much as the 3 point shot scored without missing by the opposing alliance. So, let's pretend that both alliances shoot 100 shots per match. If you miss even one shot, and you react in the fashion that will give you the greatest net gain, your score will be 300, and theirs (because of the 1 point you scored for them) will be 301.

Okay, let's interject a bit of reality to the opposing alliance. They will be missing shots too (or so everyone hopes...), or your defense should hopefully be able to force them to. Now the amount of balls on the field is far greater, and the action of the balls will have a far greater swing on the outcome of the match. For every ball they are allowed to introduce straight to the robot, they save the mandatory point cost of having their HP aquire the ball, and save the possible time of having to most to a range where the HP can shoot it (depending on the design and capabilities of the HP).

Beyond even all the net gains of each ball that is missed, there is the whole concept of ball "hoarding" when you have the lead.