If I'm wearing a seatbelt and get hit, I can be hurt. If I'm not and get hit, I can fly out and die. Chances of dying are higher with a seatbelt off... and I don't think you got the point of this original analogy, so I recommend dropping it.
You cannot strip away other reasons for making a decision simply because both have a "worst case scenario". Be a man, make the considerations and decide which to you is less costly.
For me, if my worst case scenario is I sacrifice the chargers and they didn't even stop the whole operation, then I can live with that because we still stopped this one, and I gain an alliance that eventually will keep Denerim from burning. Doesn't matter to me that the decision may backfire.
How do you walk out of your house every day? lol. Assuming you do.
All I am saying is, simply put, that making choices based off of "benefits" that have both good and bad repercussions is not so much a benefit, nor do I call them that. I think they are good reasons to make any choice, but one has to be aware of all possible outcomes before one can truly be the "best" which one has the least problems with it is a good idea, but there is more going on than a simple "the damage to both sides is better than losing 1 man" argument, as by that time, you lost quite a few people on the attack at haven.
For me, it is simply easier to make a choice based off of what is best for The Iron Bull, not for anyone or anything else, unless my character is an "inquisition first" type.