In general, graduating from an MD school will give you more options upon graduation--all else being equal. However, if you go to a DO school and do well, you will certainly have attractive options open to you.
It matters first that you get into medical school. If you dont have either MD or DO than the fellowship is a moot point. And you target medical school based on GPA/MCAT and the rest. You cannot target MD or DO based on a perception and reality that in 6-8 years down the road. So if you are a weaker candidate who gets fixated on fellowships and MD, you could find yourself wonder in 30 years why you never became a doctor.
Besides 6-8 years from now the now combined residency systems will likely lessen the impact of MD DO