Supposedly Segundo has the most active social/party scene. Its proximity to frat row has a lot to do with that reputation. But the thing is, you could have a super socially active floor anywhere, or a socially dead floor anywhere. It depends more on the people currently living there than the area itself, but you also have to figure that certain types of people are more drawn to certain areas based on their reputation, which could contribute to reinforcing its reputation.
For what it’s worth, according to a couple RA friends of mine, of all the areas Segundo (particularly the high rises) seems to have the reputation of being the most rowdy. But again, it will vary from year to year and floor to floor.
For anything else, you’d have to ask someone that requested it. I toured all the housing areas on decision day before my freshman year and Segundo didn’t appeal to me in the slightest.
And if you were going to ask why Cuarto is typically the least requested, it’s usually the fact that it’s off campus (albeit just across the street) combined with the fact that there are suites instead of traditional dorms.