I see the contrast between combat systems so far as formal patterns are concerned as a kind of parallel to the difference between two different ways of teaching morality/virtue/ethics etc. You can simply come out and tell people how they should behave, preach at them, specify exactly what they should and should not do. Or you can offer them parables which illustrate exactly the same canon of behavior, but which disguise their message somewhat and require people to interpret them. And in cases of the latter, you may well find multiple, different, but equally applicable and commendable interpretations of the same parable.
Combat hapkido doesn't have kata, but it has drills—huge numbers of very sharp two and three move combinations that you practice with a partner. As I understand it, Ueshiba's aikido also did not employ kata as an instructional tool. The partner drills these systems provide are literal instructions on what to do when, in case you're attacked; the technique of the system is therefore explicit, embedded in the knowledge of how to respond with any one of dozens of different possible responses to just about any kind of attacking move imaginable. These kinds of systems operate with combat sermons and lists of commandments. The karate-based arts, with their kata and related forms, or the CMAs with their hsings, offer you, in constrast, parables of defensive combat techniques, each one composed of subepisodes which have, taken singly, multiple interpretations, the most effective of which from the experienced fighter's point of view are well-hidden under the simple block-punch-kick appearance of the moves. Much of the previous discussion on MT that I referred the OPer to is about how to decode the kata (in the general sense) and extract the meaning, guided by the particular strategic principles of the art. The difference isn't so much a matter of content, as I see it, but of instructional technique—pedagogy, in short.
But none of it is worth a damn from the point of view of live, real-time SD unless it's practiced in a deadly-serious way with a partner who is willing to assume the persona of a dangerous, vicious attacker bent on hurting the defender, possibly gravely. There are ways to make such partner training of kata techs less dangerous, but the hazards for both the attacker and the defender are non-trivial. That's also going to be true in any of the fighting systems that don't have kata, however. Combat Hapkido, Krav Maga, or anything else designed to save your life, under extreme violence, require brutally realistic training to make the techniques encoded in their drills a reflexive tool immediately available when unavoidable danger meets you. The difference in the fighting systems is just that this has always been understood, I think, in those systems that we think of as 'combatives', like KM (and Hapkido, to some extent). The message fell by the wayside with many of the TMAs, however—but people like Iain Abernethy, Geoff Thompson, Peyton Quinn and others are teaching us how to bring it back.
