There's absolutely no reason to hold balls if you can score them in the center goal 100% of the time (of course nobody can). Then you have to figure out how many you can score out of the balls you have vs. the size of your lead. If you can score 75% of your balls, and you're holding 40 balls, thats 30 score=90 points. As I HIGHLY doubt that any single robot will ever get 80 balls, and that any alliance ever possessing more than 70 balls will be VERY rare, it may be incentive enough to try and increase your lead.
It is also important to know rougly what % of balls your opponent can score, and if it's high enough to eliminate your lead (or whether the possible 25 offensive ramp points can do it either). But if you have the lead, at some point during the match your out-shooting them, so its likely you may be able to do it again.
Few, managed to keep myself from spilling too many strategy secrets there
