I agree the whitetail is more adaptable than mule deer. They are NOT more aggressive. I live with whitetail and mule deer in my yard and my leases every day 365 days a year. I have seen mule deer yearlings chase whitetail bucks away from a food source. In my 14 years of living with them on a 24 hour day to day basis , I have only once seen a whitetail buck act aggressive toward a mule deer. When it comes to a food source the whitetail ALWAYS take backseat to the mule deer. When I feed in the winter , I have to feed the mule deer and whitetail in separate areas. The mule deer will not tolerate any whitetail--including bucks- to feed near them. I see it I live it...everyday starting at 5 o'clock in the morning. I am convinced the reason the whitetail multiply and the mule deer seem to be decreasing is the way they deal with predators. A couple years ago there were 10 mule deer does and all had twins. 20 fawns in the spring. Only 5 survived by December. I know 3 were hit by cars. Too many cats , bears , coyotes and an occasional wolf.
I can guarantee one thing...whitetail do not aggressively push mule deer from their established territory.