We seem to be heading off in a puff of logic into maybes if maybes of maybes. Would Hitler have murdered the Jews if they had emigrated? Who knows. However if his aim was from the outset to murder every last Jew in the world, then it is difficult to rationalise why many were allowed to migrate out of his grasp. AFAIK there were no German hit squads roaming the world murdering Jews en masse. There certainly were assassins eliminating people Stalin didn't like even after they had emigrated.
For me there is something more deeply depraved - therefore worse - about killing under that scenario. It's perverted in a way that killing for some instrumental reason isn't. Does anyone else have that intuition? It seems so obvious to me but maybe I'm weird.
Again, I'm afraid I don't share this viewpoint and I would reiterate that, generally, emotional reasons for committing murder are viewed as mitigating circumstances rather than the other way round. Relevant in this context is the concept of 'Black rage' for example. There is a reason why 'cold blooded murder' is a term reserved for particularly odious killings.
We seem to have ranged our discussion over a number of definitions of 'better' (and I concur with Sergey that 'better' is a strange word to use in this context). We have considered 'better' from a moral standpoint, the overall practical outcomes standpoint and the standpoint of certain groups.
To make reliable moral judgement we need to know what was in men's minds, and we will never really know that. One important issue is whether the 'accused' had a guilty mind. And I suspect psychologists will argue that one for ever. On the one hand it could be argued that both saw the elimination of 'the enemies of the state' as justified and therefore not wrong - the 'war' analogy seems to come up regularly in their utterances. On the other hand the transparent attempts to cloak their action in a veneer of legality, however thin, suggests that deep-down they felt those actions were
wrong. However, there seems little to choose between Stalin and Hitler on this score.
Motivation is another factor and here I think it can be clearly demonstrated that both men had large groups of people murdered because they stood in the way of policy; because they were a challenge to authority; because they were actual or potential competitors; because they engendered paranoia; to terrorise populations; and on a personal whim. I'm afraid that I don't buy the argument that some innocent victims are less innocent than others and therefore it is somehow morally less repugnant to murder them. I concede that people have different viewpoints on this as well as double standards - for example I am sure many people believe that it is OK to rape someone who is promiscuous but would not think it OK to rob a person who is generous. Again, sorry, but I see no reason to judge one of them better than the other.
Was one of them better because he had fewer people killed in total? That is a question on which statisticians will debate for ever and is not nearly as clear-cut as Sergey would have us believe. For one thing there is little confidence in the data and we are talking about gross estimates. The equations on which these estimates are based have so many moving parts, it is impossible to avoid likely huge error. Are we comparing like with like? Do we include just people killed by bullet, gas or guillotine? Or do we include those who died as a result of exhaustion and beatings in concentration camps? Do we include people who died as a result of forced migration? What about those who died from starvation and neglect as a result of deliberate policies with predictable outcomes such as the Hlodomor, the theft of food from German-occupied countries during the war. Or the fate of young children and dependent elders after they were thrown out on the street after the breadwinners had been murdered and their property 'confiscated'?
Do we look at the total numbers (Stalin had a much longer time to carry out his murders) or the rate of murders per annum? Raw data or per capita? Globally or from the point of view of a particular group or groups? It is this latter that seems to cause much controversy and, indeed, John2 clarifies that this is his area of his interest.
From a Jewish perspective, I think it is clear that Stalin was a better option than Hitler. However, it needs to be noted that Stalin was hardly a bed of roses for the Jews either. For a number of reasons Jews tended to be more vulnerable to the Soviet Terror than average, not least because of their culture and concentration in certain professions. After the USSR invaded Poland in 1939, the Jews in the parts annexed by Stalin were substantially more likely to be persecuted than people of other ethnicity. However, if you look at it from the point of view of many other national or ethnic groups, things look very different. And I think the point is pertinent, that while Hitler ultimately failed in his attempts to wipe out the peoples he hated, Stalin succeeded, at least in some instances. In other words, this suggests the chances of certain individuals, peoples and cultures to survive, were smaller through no fault of their own under Stalin, than those of the Jews and Gypsies under Hitler.
In summary, the old Polish adage applied to the Soviets and the Nazis as a choice between the plague and the pestilence seems very apt. I completely agree with Sergey - we seem to be having a conversation akin to whether Adrei Chikatilo was a 'better' serial killer than Ted Bundy.