This might surprise you.

On whether I am an introvert or an extrovert, I feel I am most definitely an introvert. Even though I can be very shy, this alone does not determine intro- or extroversion. Introversion or extroversion can be determined also by personal preference of exposure to people. Even though social ability is a factor in determining this part of personality, it is a very small factor. I am very creative and outgoing, but at the same time I am very selective about the amount of people I spend time with.

There really isn't any particular group that has it "easier", because either trait is "easy" to their respective person. People who prefer to spend time with other people most of the time enjoy spending time with other people, and the same case for people who prefer to spend time alone. 

The world would not be much different if everyone was an extrovert. Yet although the world would be much more interactive and connected, there would be a significant decrease in technological progress as not as many of the brilliant ideas for new technological innovations would come to mind to people who are extroverts, and even if they did, they often would not involve as deep of thought.

If everyone was an introvert, it would be the exact opposite: there would be a lot more technological progress in the various sections of the world, but yet there would be little to no connection among countries except for necessary tasks like trade. For the most part, countries would be isolationists, but within those countries there would be strong innovations.

I think a mix of introverts and extroverts are good, because even though one would want someone similar to him as a friend, it is also nice to have a variety of friends to expand one's comfort zone.

Extroverts tend to be better leaders in my opinion because they have the social skills and the motive necessary to  address a crowd of people. It is possible for introverts to do this as well, although there likely will not be as much motive. The case is the same for teachers.

Introverts tend to be better writers because in the absence of socialization, they can be affected by many other influences besides people, making their writing more varied and colorful. Plus, with the lack of socialization, there would be more time to think and to reflect upon less material matters.

In the matter of better neighbors, there are pros and cons to either one. Introverts are not as likely to socialize openly, but can be faithful friends when one needs them most, not to mention they make more "personalized" friends than extroverts. Extroverts, however, can be very outgoing, almost to the point where they're a pain to have, but one can't help but to enjoy being around them.

All in all, I think introversion and extroversion matter, because they make up a good part of a person's personality. Introversion and extroversion affect how a person acts, how he is around other people, how creative they are, how innovative they are, and to an extent how much of a good friend a person is.

Also, on an unrelated note, posting right before midnight. BECAUSE I CAN.