I am at the perfect age where I have been with both Facebook and Twitter from (essentially) the beginning.
Now I was in Junior High when Facebook really was starting, but by 8th grade we were all waiting to get into High School so that we could join the infamous Facebook.
Great stuff for a while, just like MySpace was for us in the past, Chat was a great addition.
Recently I have had countless family add me (aunts, cousins, uncles) and I like to be able to connect with them. However, in college I have found that I am connected to too many people on Facebook and have recently been "cleaning out" my friends list.
I do not enjoy Facebook as much anymore as it tends to attract ads, viral pictures (the ones with a long, heart-warming story attached) amongst other nonsense.
I do respect Zuckerberg though, guy went out on his own without talking to his board and bought Instagram. Takes some balls to walk out on the street alone (hypothetically) and drop $1 billion dollars.
I joined Twitter in December '07 just a year after it's founding. Only one or two of my friends had it at the time and we used it mostly to follow athletes and other celebrities.
Now, 4 years and 900 followers later, I love Twitter. If you see my phone in my hand I'm likely to be checking Twitter. I find Facebook to be a nuisance and Twitter to be an addiction.
I am willing to say that Twitter is the fastest way to get breaking news. Faster than text alerts, TV, internet, anything. The second I hear of something I can search tweets for it and hours later it will most likely be trending nationally or worldwide.
Great way to network, connect with friends, get the chance to connect with celebrities (I have had full conversations with the Miami Heat's Dwyane Wade, who now follows me, including wishing me a happy 18th birthday).
Twitter > Facebook