Some advice on choosing a specialization: consider the teachers whose classes you’ll need to take. Some teachers are just better at teaching than others, and sometimes even a very highly regarded teacher just won’t do it for you. It shouldn’t be the only consideration; there will likely come a time where you’ll need to take a class taught by someone you just don’t work with. But finding someone whose explanations make sense to you, whose style of teaching fits your brain, someone you find it easy to ask questions of, and taking their classes will help you learn a lot more, even if their area of expertise isn’t your first choice.