I've always liked the ability to "follow" anyone on Twitter. Unlike Facebook which I see as a way to communicate with friends and family, Twitter allows me to follow interesting people who might post interesting and insightful thoughts on topics I'm interested in. Then they limit it to the length of an SMS so I can get no more than a sound bite. I basically abandoned the platform as a waste of time.
I have loved twitter for the same reason. It has allowed me to face conversations with and forge friendships with people that I otherwise would not have met in my daily life.
You are not limited to one single tweet only. I've had multiple, meaningful conversations that span across multiple tweets. As many as needed to convey the message - not limited to just 140.
Vastly different unless the multiple sentences has a character limit. Multiple sentences tend to get lumped together in a group, let's call it a paragraph, and is easy to read in total. A thought spread out over multiple tweets with spacing between each, and in some cases broken up by other tweets, is difficult to read and follow. We'll skip over the problem of actually following a multi-person discussion in this manner.