Even though we mostly speak the same language, there are important differences between us that are the result of our different history, geography, climate and culture. Here are some of these differences:
1. The most important invasion that was suffered by the Russians was that of the barbaric, fiercely militaristic and nomadic Golden Horde. The presence of the Mongol invaders (who did nothing but burn, rape, rob, and ravage) throughout the 13th century isolated the Russians from the rest of Europe, putting them behind other European countries in terms of culture, economy, politics, religion, etc. While this was going on in Russia, a part of Ukraine was subjugated by the Lithuanians (who were behind the Ukrainians in terms of their civilization and development and quickly adopted Ukrainian culture and practices). Another part was conquered by the Poles (who were highly civilized ans sophisticated and brought European trends into Ukraine.) The consequences of this can still be felt today when the idea of being European and belonging to Europe is very attractive to most Ukrainians. Russians, however, are a lot more oriented towards Asia and view Europe with suspicion.
2. Most of the Russian lands are infertile and it is very hard to survive on them. For this reason, there were always strong communal tendencies between people who lived on the land. It was a lot easier to survive if you joined your paltry possessions with neighbors and cultivated the land together. The lands in Ukraine, however, are among the most fertile in Europe. Everything grows, blooms, and requires very little effort to become productive. This is why people are a lot more individualistic. It was a lot more difficult for Stalin to enforce collective ownership in the agricultural areas of Ukraine than it was in Russia. Also, the respect for private property is a lot weaker in Russia than in Ukraine.
3. There was a very strong legacy of democracy in Ukraine that was completely absent from Russia. Between the XVth and the XVIIth centuries, Ukrainian cossacks created a democratic government where no distinctions were made between people of "high" or "low" birth. Russians, however, were always governed by extremely autocratic rulers. This is why today, Ukrainians are still trying to establish a democracy in their country, while the Russians seem to be quite content with their authoritarian government.
4. Women always had much greater freedom in Ukraine than in Russia. Since the Middle Ages, Ukrainian women had an opportunity to choose their partners freely. Unlike in Russia, Ukrainians did not practice arranged marriages where women were not allowed to see their future husbands before the day of the wedding. The practice of having the women's side of the house where women had to stay was prevalent in Russia, but nobody ever heard of it in Ukraine. Women did not cover their heads in Ukraine (unless they felt like it), while in Russia they had to do so and cover parts of their faces as well.
5. As a result of a greater freedom for women, sexually Ukrainians always enjoyed a much greater freedom and fulfillment. The sexual revolution in Ukraine began at around 1910 (earlier than anywhere else in the countries of our Western Civilization) with the writing of one of our greatest writers (and the future Prime Minister of the independent republic of Ukraine) Volodymyr Vynnychenko.
6. Since their land was so fertile that people were pretty sure that they wouldn't starve no matter how little they work, Ukrainians became a lot more laid-back and likely to engage in prolonged spells of happy-go-lucky procrastination. You want hard-working and determined, go with a Russian. Looking for relaxed and happily snoozing on the sofa? Choose Ukrainian.