I am not directing this post and anyone. Obviously there are disagreements here about this issue. I think that it is because of at least two reasons.
First of all, everyone's experiences are different and thus biased. Everyone's experience is valid for them whereas someone else's experience may vary greatly and thus their conclusion is different. What else can one go on but their own experiences and their own preconceived ideas about what to expect in lady who comes from the city versus the country.
Secondly, there are simply too many variables that get involved. For example, one variable would be what Tootsie commented on. She said that many times the economic plight of the country girl can be such that there is increased chance of the desperation factor affecting motivation to marry a foreign male as compared to the city girl from Moscow who has life better. I think that between all of us we could come up with a huge list of variables that will affect the final equation some in favor/disfavor of the city girl with the same being true for the country girl when we speak in generalities.
Any time a person makes a statement that your chances of finding a better woman is from one locality whether it be city vs country or Ukraine vs Russia, gorgeous vs average etc., you are going to find those that would prove you wrong with their valid points.
The most likely fact is - everywhere is a good place to find a FSU woman biased only by your preferences and prejudices. I would be surprised if the percentage of educated sophisticated women was higher in the country as compared to the city. About being sincere and sweet - I am told that one can expect a higher percentage of honest sweet unspoiled women from the country and I have no reason to not believe this. This is a common expectation with many men when we discuss this. Are there 2% more, 10% or 50%? I do not have a clue. However does this statistic (whatever it might be relative to percent might be) make country women a better choice? It clearly depends on what you want. Does it make it safer to go after a country lady? This can be argued both ways and my opinion is no one knows. And if it is one or the other being safer - what percent is it?
However, I suspect that the saying "You can put a farm girl in the city but you can not put a city girl on the farm." was derived for some reason and not just pure speculation. And thus where you live as has been pointed out is very important to your choice.
So, in the city you may find more spoiled women and in the country you may find more desperate women
In the city you may find more sophisticated women and in the country you may find more women who are not as sophisticated.
In the city you would expect to find a greater number of educated women relative to the country
So, let me see if I got this straight. I want a country woman, who got a higher education in small city not too far from the farm, who now lives in the big city but not longer than a year or so - of course this formula is in part because I live near a large city but not in the heart of that city 
)
Now keep in mind this is also based upon the assumptions about city and country ladies as portrayed correctly by those here
Now what did I get with my criteria with my little bride:
A lady who got a higher education - went to the city but could not use her education - worked as a prostitute because the pay was good - developed a liking for the finer things in life but does not want to earn it this way all her life as her days are limited relative to the aging process - so she decides to marry me a USA guy - knows how be a small time girl sweet and all to attract me with her down to earth nature and also knows how to rock my world in the sack and challenge my brain with intellectual conversation after dinner.
Whoa - wait a minute you say - You can jump from one conclusion to another about who this lady is and this is getting irrelevant. - Yes to the first and no to the second count. It is people who are different and although their experiences will influence who they are - their general nature of who they really are will not change. And, every type of person good/bad, smart/dumb etc are born everywhere.
We could go on forever, one could say that until the farm girl is challenged with the city - you really do not know who she is - you could also come up with something against the city girl. THIS CAN GO ON FOREVER AND EVER.
We will never find the end to it. So, I personally am not going to worry or assume anything. I am going to judge the woman - just as everyone else here will do the same - some with better skill than others. However conceived ideas can for some cloud their evaluation because of bias. You sometimes see what you expect so to speak.
Now to confuse things even more, lets say that I marry that lady that does not tell me she was a prostitute - what could happen? Anything is the answer. The outcome could be a perfect lifetime partner who is loving and loyal - whereas the outcome with marrying a woman whose past is impeccable and on paper she is perfect could be a disaster.
So, if you think a country girl is better - go find a good one there and find her in the city if that is where you think that you will find her. She is in both places me thinks.
