...the only meaningful (albeit limited) comparisons possible are between mixed systems on the basis of their relative proportion of competing capitalist and collectivist elements. I have every confidence that comparison would favor systems such as those employed in Northwestern Europe, but it must be understood that such comparisons, conducted as to possess useful rigor, would be very, very difficult to perform.

There are so many, many variables. First off, it has to be determined what constitutes "winning" a comparison between two countries. That is, what statistically-determinable conditions are to be considered, and at what relative importance to each other. Things like average life expectancy, number of hours worked per month to obtain shelter and food, proportion of working time to leisure time, percent of GDP required to provide essential elements: a military capable of deterring invasion or fighting one off, hard infrastructure like roads and bridges, healthcare system (even if entirely private, healthcare expenditures constitute a percentage of GDP...which is why the US's is such an economic disaster), and so forth. Then there's the matter of overall happiness and contentment of the population, psychological factors that are notoriously difficult to assess empirically. Just establishing victory conditions in such a complex comparison is a massive task.

Then we get into accounting for massive differences in starting conditions between countries. Some countries will begin their move to a mixed capitalist/collectivist system with a society already deeply entrenched in an oppressive monarchial system while others are a lot closer to starting from scratch. Those vast differences have a huge effect on properly analyzing the factors mentioned above to determine victory conditions. The classic criticisms of teh Soviet Union (most all of which are valid) have to be considered alongside the inarguable fact that for the large portion of the people, things were still far better than they were in Tsarist times. That they didn't reach the level of countries in which the people had vastly better starting conditions doesn't mean the latter were automatically intrinsically superior. On the other side of the coin, the United States' starting position was set for success: massive natural resources, little likelihood of successful invasion/isolation from European conflict yet positioned to profit from them, etc. The US did well even early on in its largely laissez-faire era...but might it have done even better in terms of overall standard of living had it incorporated a more regulated, modern mix from the beginning?

This leads us to current, modern elements which must be empiricized in order to perform a proper reduction of confounding factors. As with happiness factors, different societies ability to form a sense of cohesive community varies. Look at Japan: a pretty capitalist-balanced society, not far in that respect from the outlier United States. Japan has a very market-economy-focused society with a high level of corporate political influence...yet the sense of community cohesion and collective effort is extremely strong, particularly in comparison the US's hyper-individualism. Japan may be one of the most cosmopolitan societies in the world, but it remains an Asian society, with a cultural orientation towards group effort with a high value on social harmony.

I can keep going, addressing other elements of such a study in statistical analysis...but hopefully the point is clear: this is a frightfully complicated, difficult sort of comparison to perform properly.