As with modern firearms, the common advice is to shoot the most powerful gun/bow you can be consistently accurate with. We are comparing apples to oranges a bit here in that the generally accepted minimum for hunting big game with a bow is 40 to 50 lbs draw weight, whereas the commonly selected draw weight is 60 to 70 lbs. As mentioned previous, I would much prefer my compound bow over my recurve because it has sights and is more powerful. If I had a choice, I would take the compound every time, regardless of what I was hunting for. But not everyone can draw a 60 lb compound bow, regardless of the letoff, and so a 40 to 50 lb draw weight has been established as minimums for hunting north American big game. Simply put, that is the minimum legal and ethical limit the govt imposes on the public (ethics being a subjective and personal decision). But I think you would agree that a 100 lb draw weight would be superior for hunting big game to a 60 to 70 lb draw weight, provided you can draw and shoot that weight reliably with a subsequent increase in arrow weight and broadhead size, all things being relative. Ethically, you should use the biggest/best/most powerful you can reliably shoot, and the government concluded that a 40 to 50 lb draw weight shooting a minimum sized/weighted arrow is ethically reliable enough. Lots of people hunt brown bears with 30 caliber firearms; I wouldn't consider it. That's why I have a 375 Ruger and that's all I will use to hunt big game up here with a rifle, because shooting any big game up here could result in having to also defend against a brown bear attack. My wife cannot hunt reliably with that gun/load, and cannot handle much more than a 30-06 power factor, so her ethics are necessarily at a level below mine. I'm okay with that if she is, and people do hunt big bears with even less than what she uses.

Having taught hunting ethics for a number of years, I would recommend to anyone that they learn to use the most powerful legal tool they can master to dispatch game with. Proficiency and consistent shot placement is the most important consideration, within the legal restrictions imposed on caliber/weight/power. If the weapons choice turns out to be more than you can handle, then it was a poor choice.

The fact remains that a 40 lb recurve shooting a legal minimum arrow weight and broadhead can and will reliably take black bear and cougar if the hunter does their part, as the fish and game departments in many jurisdictions have determined. It is not the most ideal choice, unless that is all you have or can handle. A 70 lb compound bow shooting a heavier arrow and a bigger broadhead is not ideal either, when compared to a 100 lb bow, unless the 70 lb bow is what you have and you can shoot it well.

In any case, I would prefer to trap big game rather than hunt if I am in a survival situation. Baiting a bear/cougar/wolf in that environment is as easy as catching a fish, and there are a number of deadfall/pit/kinetic energy trap ideas that would've been easy to implement with the materials available and a couple days of work. Whether or not a bow and arrows were brought, there was plenty of food to be had if any of them would've been willing to go after it. But again, we don't know what all the rules were on what they could do, and in a real survival situation, it would be no holds barred.