Before I made my decision to get a Doberman (long time ago) I did alot of research, met quite a few Dobes and Rotties. IMHO they both are very smart and capable canines in the "RIGHT" hands. They both can become a real handful if not trained and socialized properly.
I decided on a Doberman instead of a Rottie for a few reasons. And let me say I have no interest in showing my dog, I only wanted a loyal and loving family member.
1 - Dobermans are very clean animals - They do not slobber alot like the many Rotties I have seen and played with. Let a Rottie rub his face against you after playing with a toy or ball for 15 minutes, you will need a towell to clean that mess up.
2 - Dobermans although they do shed, they are very short haired dogs so their hair is very easy to clean up. The Rottie has a much longer coat and will require a little more grooming than a Dobie IMHO.
3 - Size - By design the Doberman is a very sleek, muscular dog that if in good health is lean and powerful. Rotties on the other hand are Bigger dogs as far as Mass is concerned, their heads and bodies are usually much larger than a Doberman of the same age and health. Their body weight in total is usually much more also.
Again theese are only my observations, both Rotties and Dobes are very trainable with the correct handler. They are both very smart and if raised properly will be great around family and children. The Doberman seems to be a little more aloof with strangers and will need to look things over for a little bit before accepting a new visitor.
And if you do decide on a Doberman be prepared to have a dog stuck to you like Velcro. Dobermans need to be with you all the time, they need to be included in your daily activities. They like to be with the family not locked up in a crate or left outside.
Good luck in your choice wichever it may be.
DA