If you're playing for the red team, then your total score is as follows
Code:
| | Play for opponents | Play for self |
|Win | red + 2*blue + 2*S | red + 2*blue + S |
|Lose| blue + S | red + s |
where S is the number of points you score for a given alliance
The decision of whether or not to score for the other guys depends not only on the probabilities of winning in each case, but the relative value of S. So without even talking about the odds of actually being able to score just barely enough to win, the decision would also depend on how many points you think you could score.