Son of Chad :
The big knives are heavy ...
Compared to a loaf of bread yes, but not to tomahawks.
Most of them are hard to sharpen and repair with what is available in the Wilds.
No more so than tomahawks, the knife is after all made out of a simiar steel assuming you are doing a fair comparison of quality versions of each.
The tomahawk can be broken down for ease of travel, and the handle can be quickly replaced with a branch.
The fit of head to a handle is a nontrivial task, it is not as similar as just mashing in a stick. To make the lock secure you need dual tapered surfaces. Not to mention the need to have a sound piece of wood as a grip, which has to be very uniform in shape and free of knots. You could of course carve it to shape, but consider the time and effort which is *much* greater than the calories burned in carrying a suitable grip attached to the head in the first place.
As for ease of carry, a big knife (~12" blade) rides easily on the hip. Large machetes and parangs can not be carried so well unless you are fairly tall, but in enviroments which demand such blades (and there are many) the extra effort in carrying them is well appreciated when they are called into use.
The big knives can cost up to hundreds of dollars, and the small knife-tomahawk combination can be gotten for under $50.
This is a very lopsided comparison. You compare the most expensive large knives with the cheapest small knives and tomahawks. You can also get large knives for less than $50 and small knives and tomahawks for >$1000 .
Martindale offers quality large knives for ~$20. Becker is a step up for the traditional bowie shape for those that wish that approach, <$100. The next step up in quality and performance would be Swamp Rat, yes you pay more but you only buy the knife once, it has a life time guarantee. The same can not be said for the $50 tomahawk and small knife.
... they do not have a finger guard which often gets in the way of intricate work
Only if the guard is very large, like on a Pronghorn for example. Even so you then have the advantage of greater security and thus a broader scope of work.
...they have wooden handles which can be replaced in the field
... and blades made out of bone so they can be replaced in similar fashion. You could of course use Micarta or G10 grips and never be concerned about breaking the grip or swelling or rotting.
As for big knives being more limiting than tomahawks, that reverse is true. A tomahawk will only out perform a large knife in cutting very thick woods, wood which outside of dedicated felling (gathering winters wood) is never cut in survivial or general outdoors work. Quite frankly the danger of felling trees increases massively as the tree size grows, not to mention the utility value is much lower (much harder to burn, to move, and to shape).
Green wood, even of small size, 3-4 inches will burn long into the day (even in a very hot fire, and of low quality burning wood like pine), so there is no need to whack down a 12" tree to make a camp fire, nor build a shelter. You don't need to cut down 75' trees to build a leanto. Houses are made using only 4x4" for the thicker beams, there is no need to even go this large for a shelter.
Outside of cutting or splitting such thick wood, the knife has a clear advantage over a tomahawk (which is vastly inferior to a quality axe anyway) and is much better for any utility cutting and leagues ahead for clearing light brush, which is critical for gathering food, insulation for the shelter, supplementary clothing, and bedding materials.
As for natives, look at native large blades such as parangs, goloks, machetes and khukuris to name a few. Consider as well than in many cases natives don't always use what is most efficient, but what is available (monetary restrictions) or what is traditional.
-Cliff
Sounds like you've had some interesting experiences learning by living.
