One cannot say one method is superior to the other. Both have different syntax for doing the same things like initializing state, defining properties, etc.
If you use React.component, you have to use something like babel to transpile the code to es5. Because class keyword is part of es6 and not supported by all browsers.
Facebook might have plans to remove React.createClass in future. But, you are good to use it for now.
Finally, it all comes down to preference. Use the one which you feel more comfortable with and don't mix both in a single project just for the sake of simplicity.