Hello sir. NDA or National Defence Academy Exam is a national level exam organized by UPSC (Union Public Service Commission) to recruit candidates in Army, Navy and Air Force. It is a two-tier examination, wherein, candidates qualifying the written test will also have to clear the SSB interview round. AP EAMCET 2019 is scheduled in the month of April in two sessions. Indian Nationals satisfying local/ non-local status as laid down by the Andhra Pradesh/ Telangana Govt. can apply for the examination. Now the decision is entirely yours as both are on the same date like you said. If you want to go for defense, go for nda or else eamcet. Best of luck.