I have to disagree with your assertion that the soundest field in CS is graphics. My field is algorithms (in particular, numerical and algebraic algorithms): I describe a problem, describe an algorithm, prove that the algorithm works, prove the algorithm's running time, implement the algorithm, and then write a paper saying "look, my algorithm is faster than that other guy's algorithm". What could possibly be sounder than experimental results backed up by rigorous mathematical proof?
As for picking a supervisor vs. picking a university -- I agree with this with one very small caveat. If you don't need any supervision -- by which I mean that you've done independent research before and have a good idea of what research you're going to be doing as a graduate student -- there's really no need to pick a supervisor. My supervisor, Richard Brent, is one of the greatest people in my field in the world; but this was entirely coincidental, and in my time in Oxford I probably saw him an average of once every three or four months. I could have been at the University of Timbuktu (if there is such a place?) and received adequate supervision; the greatest benefit Oxford provided to my research was to open doors for me -- it's amazing how many people pay attention to an email which starts "I am a doctoral student at Oxford University".
One final remark about supervisors: If you're planning on applying to do a doctorate and there's a particular professor whose research interests you, you should absolutely contact them; if you're planning on applying to do a master's, please don't. There are far too many wannabes with no research experience entering master's programs to have a personal dialogue about one's research with every one of them.
As for picking a supervisor vs. picking a university -- I agree with this with one very small caveat. If you don't need any supervision -- by which I mean that you've done independent research before and have a good idea of what research you're going to be doing as a graduate student -- there's really no need to pick a supervisor. My supervisor, Richard Brent, is one of the greatest people in my field in the world; but this was entirely coincidental, and in my time in Oxford I probably saw him an average of once every three or four months. I could have been at the University of Timbuktu (if there is such a place?) and received adequate supervision; the greatest benefit Oxford provided to my research was to open doors for me -- it's amazing how many people pay attention to an email which starts "I am a doctoral student at Oxford University".
One final remark about supervisors: If you're planning on applying to do a doctorate and there's a particular professor whose research interests you, you should absolutely contact them; if you're planning on applying to do a master's, please don't. There are far too many wannabes with no research experience entering master's programs to have a personal dialogue about one's research with every one of them.