I can tell you one thing, the TKD kicks and punches I learned and eventually taught depend on explosive hip rotation. There's a linkage of movement that begins in the stationary foot and ends at the delivering hand/foot. This chain of motion is also the most difficult aspect of TKD to get right, which is why there's no shortage of TKD practitiioners making the techniques look bad. Not to mention, most of those that would make the techniques look as good as they are have too much traditionalist pride to fight/train in MMA. That has changed a lot in the past few years, though, as more and more TKD schools are adding MMA programs.
A well-rounded MMArtist with TKD technique, speed, timing and fighting intelligence is hard to beat. A TKD practitioner who has little experience outside of WTF or ITF (especially
) rules sparring will likely get destroyed when he leaves those rules behind.
A properly timed axe kick will easily break a collar or cheek bone or lead to a KO. A poorly timed one can lead to bad news for the guy throwing it. A turning back side/hook kick used to counter an opponent's attack can be devastating. Leading with it leaves you incredibly vulnerable. A lead side kick with proper hip rotation can break a rib and prevent a puncher from ever setting his feet. Without the hip rotation, the guy getting kicked can literally knock the kicker down just by standing his ground. Failure to properly chamber and retract any of these kicks properly is asking to be taken down.
With TKD, it's not the techniques that fail, it's the people trying to use them. Of course, that's true of any combat style that survives any length of time. The key is to find the style that fits your personality and body and make that your base. Mine is definitely TKD.