There is much debate, often very heated, about survival kits. Most every bushcrafter has opinions about the "best" size and contents of the kits, and there are several different philosophies regarding kit design . Some folks are minimalists while others prefer to kit-up to survive indefinitely in the wilderness. Some are enamored with the "Altoids tins" while others prefer surplus pouches.
I will not be so presumptuous as to say one kit or philosophy is right
or wrong or that my kit is the best. However, I will say that the kit
that you choose must suit your specific needs. This means
that your kit(s) should be influenced by your: knowledge and experience,
location and environment, and the typical circumstances in which you
enter the woods.
A survival kit, like any emergency tool, is only useful if it is always
available. Basic items should be carried on your person every time you are in the woods. Every time, without fail. It is absolutely imperative that basic survival items be on your person so they are always available. I carry my basic survival items -the bare minimum kit to get me through a 24 hour situation- on me in the same manner, in the same place every time I'm out. I choose to carry them on my belt and in my pants
pockets because I can envision many scenarios in which I could be separated from my pack or other gear, but
very few in which I would loose my pants. Having said that, you could just as easily carry them around your neck or in a belt pouch... the important thing is to alway carry them on you.
You are much more likely to carry a small item that is
comfortable than a larger item that causes discomfort, no matter how
important that item may be or how much more preferable the largre item may
be. I liken this to concealed pistol carry: when shit goes down a smaller gun on you is better than a bigger gun left at home. For me the ubiquitous Altoids tin is too small, too rigid and not comfortable to carry...so I have packaged my kits in simple bags. But that's my preference, and many people carry tins comfortably. It comes down this: the more comfortable it is to carry, the more likely you will be to carry it. The key here is to find what works for you and always carry it.
Ultimately, the best kit is the one that you have when you need it.