How to choose a speciality for Externship



I will be doing extership after my final year exams but am unsure between EM, IM, PSYC and PEDS. How can I get a better idea BEFORE applying for a specific extership? I don’t want to choose the wrong one based on the stuff I see on TV (EM is very attractive…But will I suffer from burnout and how will I balance work and a family)