Here's my impression of cities the OP mentioned:
Tokyo: If you're learning standard Japanese and/or want to sound like actors in Japanese movies/dramas, this is THE place you should go to. Since you're already learning Japanese, I think you already know what it's like. It'd be the best pick unless you don't like a big city or have a special reason to study in another city. You'll have a lot of fun there.
Osaka: One of the biggest cities in Japan, and it's a very nice place to have fun. While vocabulary, grammar, and pitch accent of the local dialect are different from standard Japanese, most of the Japanese understand it. Actually you'll often hear actors speak or fake the Osaka dialect in TV shows, movies, and so on. This is the only non-standard dialect that you can safely pick up without worrying if native speakers from other regions understand you, though you might have trouble understanding them if you don't learn standard grammar at all. A stereotypical person from Osaka is friendly, extrovert, and always telling funny jokes. If you're a guy, you can take advantage of the stereotype when you visit other regions, if you know what I mean. たいがい and なおす are examples of rare words that guys from Tokyo would be confused by. I was born in Osaka, by the way.
Kyoto: Very old city that used to be a capital of Japan. If you're interested in traditional Japanese culture, this is one of the best places. It's next to Osaka, and its local dialect is very similar to the Osaka dialect.
Nagoya: A major city that has its own dialect. Older people have a stronger accent. It's not unintelligible or anything, but if you speak Japanese with the local accent, you may have difficult time making yourself understood more often than if you speak standard Japanese, especially when you talk to people from a completely different region. Nagoya is a fairly large city, and it's a nice place to stay for a longer period of time. If you don't like urban life, you may not enjoy this city.
Fukuoka: A major city in the Kyushu region. The local dialect has a stronger accent. I have a friend from Fukuoka, and sometimes I have to ask the meaning of a non-standard expression he uses. If you don't want to acquire a strong non-standard accent, you might want to pick another city, though it's nice to learn the dialect. I've heard a lot of good things about Fukuoka, so it should be a nice place to live in.
masaman Wrote:More reserved/traditional people, you can find in 東北 area.
Definitely! Aijin is from Tohoku and she's really reserved and traditional!!