Is it better for your hair to straighten it or wear it in a ponytail?

ok i had long hair that had a little wave but wasnt straight and i got it cut last july and donated the 10 inches tro locks of love.after i got it cut and it grew a little bit,it started to get kinda spirally curls,but mainly just around my bangs.so usually if i didnt scrunch it(which i dont really like to do since it makes my hair ratty) i would just brush it out and put it in a ponytail.but i know that if u wear your hair in a ponytail everyday it can be very damaging and can make your hair thinner in the long run (oh and i have like medium hair thickness).so i want to wear it down more but it doesnt look good unless i striaghten (flat iron) it.SO HERE IS MY QUESTION:would it be less damage on my hair to straighten it everyday and leave it down than to brush it and wear it in a ponytail?