Jiu Jistsu or Muay Thai?

ok so im 15 and just recently wanted to get into a martial art these are the only two im intrested in.I want to do this to get in shape and learn how to defend myself i know muay thai you can wear shorts over that other thing like the robe i dont really like that but thats not deciding for me i want also do muay thai because i have a little Thai in me. my only concern is i wont learn anything of grappling on the ground so im guessing if i go to the ground i lose any way i dont want to go into the mma i just want to do it, but in professionals when the two arts fight who normally wins ive checked out videos and it seems even but i want your opinions thanks