Size
The Rottweiler is a little larger on average: about 45 kg (99 lb) as an adult, against 38 kg (84 lb) for the Doberman Pinscher.
Shedding
Their coats shed differently: the Doberman Pinscher sheds through the year, the Rottweiler moults most as the seasons change.
Grooming
The Rottweiler needs more grooming, brushing a few times a week, where the Doberman Pinscher needs a brush once a week.
Exercise
Plan for plenty of exercise with the Doberman Pinscher, and a moderate amount with the Rottweiler.
Temperament
They differ most on sensitivity (Doberman Pinscher: needs a calm, predictable home; Rottweiler: hardy, takes a busy home in its stride) and on independence (Doberman Pinscher: keen to work with you; Rottweiler: cooperative, with its own ideas).
Alike
Both are rated the same on affection: a lap or leaning dog.