i dont think you need either, why would you? to apply? obviously it would look good/give you something to talk about if you've done more than just your standard required rotation in neuro... i havent done my medicine sub-i yet etc..
do whatever subi you want, it doesnt matter. you do a year of medicine anyway. as for me, i may very well do peds or family practice or maybe even surgery subi. why not? last chance. as you can see, ive had to change my schedule a lot because of these interviews.