I really don't think socialism works on a large scale. I can see the emotional appeal and it would probably be great to operate that way within tribes of maybe 200-300 people, which is probably the type of setting early humans evolved in. But on scales of cities with a million people and countries with hundreds of millions, I'd have to say that a meritocratic system works better.

If you look into evolutionary psychology, there are two ways humans will naturally use wealth to show off: by spending it like water ("luxury" apartments, buying your bride a diamond ring, etc.) and through charity, by being generous with it. What we need to do is try to change the culture, emphasizing charity over consumption. This won't be perfect, but I think it's better than taxation. First, it has a benefit for the person being charitable, whereas nobody feels philanthropic about filing their tax return. More importantly, you can have two charities for feeding the hungry, and if one sucks and is a bureaucratic, completely inefficient money-waster, you can support the other one. This is big. In contrast, if government bungles the program, your money is taken and wasted, and you have no recourse.

Also, while a market economy allows people to act in relative freedom, socialism is based on forcing people to share. I'm not saying this is a moral argument against socialism, because I'm aware that that reasoning is culturally biased (to someone more collectivistic, it might sound ridiculous). Rather, it poses a practical problem. You have to have someone who enforces that sharing, and you get into a "Who watches the watchers" problem -- not everyone can be ruled by force; someone has to be in charge. These are ideal conditions for a despotic ruler to come to power, as has happened with communism.