[...] he is either a sociopath or a psychopath. (Psychopath being the preferable assumption.)
'Sociopath' and 'psychopath' mean very much the same thing. If we were to ascribe medical conditions to the characters, I think Todd would be eligible for a mild psychopath label. To his credit, though, he is not cruel for no reason. He does what he deems necessary; thus he can spare Skyler, whereas he needs to remove Jesse's remaining link to hope.
If I am not mistaken psychopaths are born and sociopaths are made (due to environmental circumstances).
Nico's right insofar as anyone has a clue what they're talking about with respect to this subject.
There is no official definition of the difference between a psychopath and a sociopath, and some say that the terms are largely interchangeable. In fact, the The Diagnostic and Statistical Manual of Mental Disorders (DSM) lists both psychopathy and sociopathy under the heading of Antisocial Personalities. Both psychopaths and sociopaths engage in similar actions and tend to have similar characteristics. The idea of psychopathy is older than that of sociopathy, and has a more defined means of diagnosis. Some differentiate between these conditions based on their proposed causes, but others disagree with this method, as the causes of both conditions are not definitively known. Additionally, both of these conditions are generally considered to be different from psychosis and Anti-Social Personality Disorder (ASPD), though these terms are sometimes associated with them.
I don't think that he made any claims regarding cause, just that the terms are interchangeable, as oppose to the hard, fast distinction you appeared to be subscribing to. Speaking just in terms of the original discussion regarding definition, his statement was more accurate--the two diagnoses are effectively interchangeable.
You also left off this part when quoting my source, btw:
as the causes of both conditions are not definitively known
Little does he know I have a machete in my Chanel bag
That makes sense (although, going by the proposed difference between the terms and what we know of Todd's family, I would disagree). I only quoted you because I thought you had your concepts mixed up, giving psychopathy some kind of moral benefit unknown to the rest of us.
Todd is absolutely amoral IMO. He's completely motivated by self-interest. Guilt/regret are not in his vocabulary. He respects Walt (as his own self-interest is only exceeded by Walt's) and knows Walt's power which is why he spared him and then didn't kill Skyler, I think. That's established in the scene a few episodes ago where he's describing the train heist to his uncle. He does not respect Jesse (who cries when describing things Todd is proud of, like killing the kid- did you see his face when Jesse talked about that in his confession video?) and so had no such reason not to kill what'sherface at the end of last episode.
I kind of see Todd as the young kid trying to impress his partners. I honestly see him as more of a follower, as he doesn't seem to have much motivation behind his actions other than to win the admiration of either Walt or his Uncle. The more I think about him, the more I just see him as coldly rational, obedient, and appears to lack a genuine sense of empathy (and that's almost entirely assumed, as he does at least appear to utilize common niceties, even though what appears to be half-heartedly, it's not like he does so for any sense of personal fulfillment). Even with killing the kid, he was technically right in that no one was supposed to know the train was being ripped off, and from a logical perspective, all his actions make sense. I think there's some amount of good to Todd's character, despite how aloof and eccentric he appears-- He's never killed anyone with a purpose behind it.
As far as labeling him a full blown sociopath, I don't really see anything that he himself is looking to directly benefit from any of this besides what appears to be fulfilling a need for praise and a sense of belonging -- About the only thing we know Todd himself wants independent of anything or anyone else is a romantic relationship with Lydia, and even then it's only implied (although glaringly obvious).