Papers. With papers you are actually applying concepts you have learned in a constructive way, and are forced to think critically about the learning material. Plus you have time to prepare and make sure it's perfect.
With exams a lot of the time you cram, throw it all on the paper, and then forget it about it a day later.
Although I hate writing, I'm a really good writer so papers are easier for me to deal with. I'm a major procrastinator and that is a total no no when it comes to studying for an exam. So pretty much, I've failed exams before but I've never gotten below a B- on a paper