I was kind of undecided to enter research program half time or just study and pass the courses in grad school because I heard some rumors here and there that doing research makes studying basic materials harder. and it does make sense since when you enter a research program you are concentrated on something and you would not be in the mode of studying a wide range of physics materials except the ones that covers your special research. this was strengthened when I read about it in the Berkeley website.
now I want you to share your prospect. when do/did you take the Qualifying/preliminary exam and how do you deal with grad research when you want to get ready for Exam?