tx differences ????

what is the difference between the dx3s and the dx3r ? there's a huge difference in price ! but what else is there ? help me out here guys cause ive tryed this 2.4 stuff before and couldnt get my tx and rx to bind correctly so i went back to my m8 and xxtra recievers . and now im looking at the dx3r , and then i come across a dx3s for a hell of a lot less