Both breeds are very similar and were bred for pretty much similar reasons and equally give as much love as the next dog, but dobermans are very much more involved with their owners type of breeds as they are known as "velcro dogs" and they thrive on please and being with their owners.
It's juts a matter of preference really, again if it's your first as you've probably been told that females are a good choice unless you have experience in dominant breeds that will test your authorities (male dogs more so than female).
What ever you choose im sure it will be the right choice, just do plenty of revision beforehand