I love watercolor paint for its unpredictability. I can try and create a certain design using techniques, but you never really know what you'll get until after you have laid down the paint. The variety of colors, gradients, and designs I've discovered with watercolor keeps me coming back for more. It's like the Grateful Dead's music; you never get the same thing twice.
On a more practical note, watercolor paint has no smell. Unlike oils, where you have a strong smell, watercolor smells like nothing. Acrylic paint also has no smell, but you can't get the color gradients and playfulness with acrylic.
The first time I tried watercolor paint was in college. At first, I was frustrated that the paint would not look like what I was trying to paint. My professor wasn't a fan of watercolor paint either, but encouraged me to keep trying and to have fun with the paint. It wasn't until I would wash an entire page with color that I realized the potential of watercolor paint.
My favorite watercolor paint is Windsor & Newton. I like this paint because the pigmentation hold up very well over time and stay vibrant. The colors stay true to expectations. I use the kind that comes in the tubes. You can pick some up online here.