UCR are what us North Americans call the true form. Plain old craniifer are what Europeans call the true form. It's really a preference. I personally like UCR because of the jet black look to them and the awesome pronotum markings.
Roach Crossing has B.craniifer "UCR" and B. craniifer "Orin McMonigle". I've also read about the "European brown-wing form". There seems to be a lot of debate as to whether or not the "European brown-wing" is truly B. craniifer. I can only speak for the "Orin McMonigle" strain since they're the only Death's Heads I own, but the "Orin McMonigle" B. craniifer are really attractive with dark tegmina and very distinct pronotal patterns. They're also very skittish ,and I can't pick up adults and larger nymphs without getting a few little pokes and scratches. The info up on Roach Crossing says the "UCR" strain is darker, larger, calmer, and with less distinct patterns on their pronotum. I'm sure Roman could confirm that for us though, and let us know what you decide