Good question! Which one is better seems to me like a judgment call—you have to decide which system lines up most closely with your values and the qualities you would like to see in your society. Here is a quick recap of where the two planets stand.
Urras is comprised of a number of different countries with their own values and political systems. Anarres, by contrast, is populated by just one group: the Odonians, who left Urras over a century ago to form their own anarchist/communist society, and have since had little contact with the other planet.
Anarres is an egalitarian society opposed to "propertarian" thinking; nobody owns property, and there are few officials with any power to coerce citizens. Wealth is shared (existence is spartan), family ties aren't prioritized, and while there isn't much of a legal structure that forces people to act, societal expectations are strong enough that most conform to them. Though this is an effective environment for many, some, like the young Shevek, find themselves limited by the one-size-fits-all attitude; a genius, he dreams of a place where he can explore (and express) his theories freely and exercise his individuality (something the education system on Anarres doesn't typically focus on). Work on Anarres is typically menial; Shevek is one of the few to escape to the somewhat better-off capital, where he gets to work at the National Institute of Sciences. Even then, however, upon the advent of a drought he loses his position and is sent to do manual labor in terrible conditions—he has little say in the matter. Sexuality on Anarres is relatively free and open; social pressure keeps it this way, and tends to look down upon those who, like Shevek and Takver, want to form a permanent partnership.
Urras, by contrast, is made up of different countries with different political systems. One of the most powerful is A Io, a country that at first appears opulent and rich to Shevek, who is kept from the poorest areas of the deeply stratified country. While he has his intellectual freedom and all the resources he needs, he recognizes that the lower classes are terribly oppressed. He also comes to the realization that politics on the planet are unstable; a war breaks out between A Io and Thu, and Shevek fears his discoveries will be used to wreak destruction, not help those in need. The intellectuals around him are all part of the power play—they don't work just for knowledge, but for political and financial gain as well.
Identify at least 5 social norms within Urrasti society.
Identify at least 5 social cultural values within Urrasti society.