Arlington planned for each of the Orange Line stations to have a different vibe, and they have indeed evolved that way. (Here's another discussion thread with some comparisons.)

As mentioned above, each station is about 1/2 mile (10 minute walk) apart.
- Rosslyn: high-rise, high-rent office district, can walk to Georgetown or Kennedy Center
- Court House: leafier residential area, convenience retail (and cinema) in government office complex above station
- Clarendon: lively nightlife and dining hub, lots of daytime retail as well
- Virginia Square: high-density residential and some institutions (Arlington library, George Mason Univ., FDIC)
- Ballston: high-density residential and office, "last stop in the city" before suburbia starts to its west

Locally, Clarendon has a similar social stereotype as Hoboken or Lincoln Park or the Marina -- i.e., full of bro bars. There's more to it, but as others have mentioned, it's pretty overwhelmingly 20-somethings at night.