The Rapid Deployment I'm aware of (its stamped on the blade) is also called the RCM or Recon Combat Machete, though for all I know, Newt stamps "Rapid Deployment" on all his knives...
Lets see... The HKR is the same length (roughly) as the Busse Steel Heart. It is thinner, lighter, and more oriented to combat (specifically sentry elimination) than is the Busse, but it also doubles as a general purpose large camp/utility knife.
The RTAK is Newt's answer to the Busse Battle Mistress. The same length, but again a little thinner and lighter, a good chopper and again camp/utility knife.
The RCM is a machete. Longer than any of the others it is the best machete I've ever owned. The HKR is too short to be a machete. The RTAK is long enough to be a machete in a pinch, but the RCM is the real McCoy!