I own both. Although there can be some colour variations, nowhere near as much as the larger beardies. Although I think the Pogona mitcheli do colour up, but not really the Pymgy or Dwarf. With some selective breeding this will improve over the next few seasons I would think.
Differences, well I think pretty much the only differences between henrylawsoni and minor are patterning (I think minor have nicer patterning), and I'm pretty sure the minors tails are slightly longer. My Dwarfs are still young (a few months), and I have found they aren't as timid as my Pymgys were when they were young. The Pygmys want to get off my hand, but I have trouble getting my Dwarfs to get off! Not sure if this is a difference between the types or if in this case its just a genetic thing that they are calmer or what.....
If I was to choose between them, I'd go Dwarf (minor). They can be harder to find though and a lot of the ones I have found up for sale as 'Dwarf Bearded Dragons', with a bit of probing of the seller, are actually henrylawsoni - many aren't aware that there is another type thats a real 'Dwarf' and they wrongly refer to Pygmys as Dwarf.