Semper Fi,
First off, welcome to the forum! Here are a few things for your consideration.
One, the kukri models made today are mostly what you would consider farm tools and utility knives. The days of the large thin bladed kukri [13-15" blades] designed as a primary weapon or primary back-up are long gone. With the advent of the firearm the weapon role of the kukri drastically diminished and now even the military issues are more of a utility knive and cerimonial weapon, much like the USMC Ka-Bar is. That is not to say that they cannot be used very effectively as a weapon but, so can a hatchet or a folding knife or your e-tool. The overall plan has to go drastically wrong if you find yourself in a knife fight, if you catch my drift.
Here on this forum we more or less buy, sell, trade and share our passion for the kukri, you won't find many "cut your head off" type of posts. But to answer your question, you will find that even the relatively small BAS model [10.5" blade, 14" overall] will be more than adequate in a self defence role. As a general rule, the kukri that are considered mostly weapons are long, light, fast and have a thin blade (relatively speaking). One of the favorite models in the martial arts community is the Sirupate. Other models to consider are the M43, which is a type of old MkII from the WWI / WWII era and the BAS I mentioned above.
Although it is common for people to fixate on "BIG & heavy" I would recommend going in the exact opposite direction, light and fast. For that reason I would stay away from any of the models that are considered heavy choppers and even stay away from models with military names such as the WWII, which in its current weight and configuration is not even close to a weapon.
As for your question about the Ka-Bar and the Cold Steel you will find that it is sometimes hard to get a real answer on some of these forums, especially when you consider that they are funded by manufacturers. But they are completely different animals and in all reality there isn't much in the way of competition between them and the traditional kukri. But here is my take. The Ka-Bar isn't really a true kukri but rather a kukri machete. Meaning that it is a heavy machete that borrows the shape of the kukri. Of all the kukri machetes out there the Ka-Bar is just about the finest and can probably be considered a true hybrid of the two rather than a machete. But a very nice, cost effective blade. With Cold Steel you have a few choices, going with the kukri machete which is a close second behind the Ka-Bar or going with the full Gurkha Kukri. Without doubt, the SK5 and VG1 Gurkha Kukri are the finest production kukri you can buy from anyone at any price. And they are very much designed along the lines of the old MkII's, that is to say they are weapons. These modern production kukri models are what is sometimes referred to as kukri-like-objects or KLO's. Meaning they are not traditionally hand made like the ones from Nepal and India.
So why is that such a big deal? The traditional kukri is made one at a time by skilled hands and shaped and hardened to accomplish certain tasks. The blade is hardened to three different levels so that the spine is softer and flexes when doing heavy chopping while the edge is harder to hold en edge but, not too hard that it cannot be sharpened easily in the field. Weight is placed in different areas for heavy chopping, light chopping and utility work, all under the skilled eye of the kami (blacksmith). The production kukri is cast from a mold, hardened the same throughout and no variationin size or weight. The blade is so perfect that it actually negatively effects performance by making the blade stick, much like a machete. The hammer marks and imperfections in the traditional kukri blade help to keep the blade moving through wood and the extra weight placed in the belly of the heavy choppers means that the blade does the work, not your arm.
So in the end it is up to the individual to decide if they like the modern production kukri or they want to experience the hand made masterpieces that HI brings out of Nepal. One thing is certain, they will all put a hurting on the boogyman!
