The question for the shelter is: how much better does the C shelter really make the situation?
I believe it provides a VERY SIGNIFICANT advantage. First off, it is immediately available; which is important because you very vulnerable at the onset. Instead of worrying about building a shelter, you can search for water and food. So it is a huge time saver. Second, the other two groups don't have any good tools to create a decent shelter. Just what do you think you can build without a good cutting tool?
Ignoring the fact that it is immediately available, I think the quality of the shelter also plays a huge role as well...
- it provides you with a place to get away from 99% of insects. Any shelter built in groups A or B will offer very little protection against insects. Not only are insect bites annoying, itchy and troublesome, they can also be dangerous due to infections, etc.
- it provides 100% protection against wind and rain. Scratch built shelters will always be vulnerable to heavy winds and may not be 100% rain proof (especially in the presence of heavy winds)
- it provides you with protection against wild animals. It will take a very long time and a huge amount of effort to fully fence off a scratch built shelter in order to protect it against the vicious animals (especially with no cutting tools!). Many such animals hunt at night and pose a significant threat. With group A at least you have the rifle and 3 people to take turns standing watch, but it is still far from perfect. Group B is extremely vulnerable. With the ready built shelter, you have a safe and secure place.
- wasn't filled with three tons of weed that you have to get out, alone to boot.
Luckily we have time! That is of zero concern for me. That can be accomplished once all the pressing matters have been addressed (acquisition of water, creation of weapons and traps, further securing my living area and making fire). At the beginning, all you need to do is make sure you have enough room to sleep.
In fact, all that weed would be useful. I would use the packaged up bricks of weed to line the inside walls of the shelter to aid in insulating the shelter (seeing as I have 3 tonnes of the stuff).
- had a hole in the roof (yeah sounds weird, but one of your problems will be getting cold, even in pretty warm climates. You have to make the fire close to yourself, inside the shelter, so you can be dry and warm).
The last thing I want is to have a hole in the roof. One of the key aspects of the shelter (as opposed to scratch built ones) is that it offers full protection from wind, rain and animals... plus near perfect protection against insects [because a few of those bastards will always manage to get in!]. As I mentioned above, the weed can be used as an insulator. If I am still cold, I could use the sails from the sail boat as a make shift blanket (without damaging or altering them, so that they are in perfect condition for departure in 12 years). You'll find that your scratch built shelter and fire are pretty useless in a tropical storm!
Also, there is no way I would risk my shelter by setting a fire inside of it.
- was portable (not important short term, but can become very important for long term survival).
No worthwhile shelter is going to be portable. It would serve as my primary base of operations. Slowly I could create further barriers and water collection systems. I could create workstations and tools. All these require a stable and fixed base.
If the time comes that I need to move for some reason, Group C with the knife is in a far superior position to create a secondary (temporary) base. All this depends on how big the island is in the first place.
For the most part though (there are exceptions), I think the better strategy is to largely stay in one place and cultivate and transform it to suit your needs. If you are moving around you will only ever have the most basic of shelters or equipment. Plus all that moving eats up precious calories.
The knife is great but you can survive without it until you can improvise.
In fact I read about some survival guy who said he'd ditch his knife way before he'd ditch his axe.
The knife is often considered to be the premier survival tool. You may improvise something in the other two groups, but it will always be a very poor approximation of my knife in group C.
The knife vs. axe argument is a moot point, as no group has access to an axe. Both and axe and a knife are immensely useful tools. The axe will be superior in terms of felling trees, while the knife will perform better with finer tasks.
the shelter is by far the best thing in C
The shelter, knife and sail boat are all exceptional. The only things that come close is the booze from group A (for the bottles, disinfecting, fire starter, etc.) and the freezer in group B. Even still, I probably wouldn't trade away the knife/shelter/sailboat for any of the items in group A or B.