From my experience as coach and strategizer for our team at two regionals, it always DEPENDS. One strategy will very very rarely work for all matches in this game; you have to take each match as it falls out and go from there. Our robot can play multiple roles on an alliance: if we have a good shooter on our alliance, we can play defense and dump a bit, but if we're the top shooter on the alliance, we can shoot quite well. We're an all-around robot, basically. So for our strategy...
Say we're with two dumper/defenders. We'd be the primary offense, ask the others to play defense for us while we shoot, then go for the ramp. But what if we're with two good shooters? We'd play defense with the better pusher of the other two, and we'd block for them so they can shoot effectively.
What about the opponents? If you're against two or three shooters, you concentrate your defense on the center of the field. If you're against three dumpers, though, you sit in front of the corner goals. If your opponents can't push well, defending your scorer isn't as crucial; but if you're up against a minitank, you keep them away from that shooter at all costs.
My point is, it depends on your alliance partners' capabilities, as well as those of your opponents, as to whether it's better to stop the scoring of 80 points or to score those 80 points yourself. Due to all the headaches trying to strategize before the competitions, I've decided "Case-by-case basis" is a great motto for this game.
