I agree with Geodome. Don't ask us to tell you what to do, you have to find something that you are interested in and something you want to do. Grad school is a big commitment of time and effort, so you want to make sure you pick something you like so you aren't miserable for the entirety of you studies. There will be good times and bad times in any research program, but it's a lot easier to get through the tough times when you are interested in what you are doing!