Is it better or worse to go to a DO vs an MD?

I'm a 6'1" male, around 280 lbs. I'm trying to schedule an appointment with a CRS for what I'm worried is a fistula. I went to my GP, but he referred me to a gastro. I've been told by other people who've had fistulas that I need to go to a CRS for this. My insurance says I can self-refer, so I'm trying to schedule an appointment with one. Is there any difference between going to a DO vs an MD? Is one worse than the other?