I'm concerned with the reasons too, although they may change with some research and help. You may decide this isn't the breed for you, if you look at everything and be honest with yourself. Or, you may decide that yes, this does sound like a great breed for you and you can learn first and do things right. If you are honest with yourself and really look at all the angles, not just the surface ones, (cool looking, tough etc) you will probably do the right thing for yourself. Spend the time researching first. Don't rush into a decision that can cost you huge heartache down the road and hurt another living and innocent being.
Dobermans are not like a lot of breeds. They're perky, high energy and demanding. And most Doberman experts advise not getting one as your first dog. Now, I know you said you had a couple dogs when you were young. But have you had the practice in training a dog as an adult? As an adult, I would recommend starting with an easier breed. And if you do get a Doberman, a female is easier than a male. (in general) An older rescue might be a better option than a pup. But be careful what they give you. Make sure they have a reputation for matching owners and dogs well. Some do not.
Most all dogs will alert you to danger...to a prowler. It's in the canine's make-up to protect his family. My Chihuahuas make more racket than my Doberman...can hear things further away and sooner than my Doberman. It never fails. I have a .38 in my drawer and I have no need for a Doberman.
I would hate a dog who scared people on account of his behavior. If they're worried about my Doberman, Lyric, it's on account of the breed's reputation....not much more. (except for a couple of occasions where something weird did happen and he went in front of the door and growled) But that's when I was in the shower and alone in the house. He was out in the yard and some man he didn't know came over. He was fine with him in the yard, but when he approached the front door, Lyric scooted up there, sat in front of it and gave a little, throaty growl...not a big to do, but just a little warning growl, where by the guy went further back on the path. Then when I came out, he told me all this. Then Lyric was friendly to him. But he doesn't have a problem with delivery people, nothing. He's definitely stable and not indiscriminately flying off the handle. Part of it is his temperament and part of it is his socialization and training. Without ample socialization, a dog doens't have a clue.
He doesn't bark as much as a lot of dogs. For example, when we're all outside and someone drives up my long driveway, he doesn't bark at all. He just stands there, "duh...." He watches quietly. They can get out of their car and he just mozies on over to see them. He just watches. He's not particularily outgoing at first but not aggressive. If we're in the house, they all bark. But he doesn't bark anymore than any other dog I've ever had except for my Lab. I don't want him to scare people.
When we're on an off leash hike in the woods and we occasionally happen on some other hikers, he minds his own business and isn't concerned with them at all. That's how I like it. They're not doing anything wrong and he knows it.
I hike with my dogs almost every day....a little less in the hot whether. Dobes are not cut out for extreme temperatures and can over heat easily. But they need off leash, good aerobic exercise every day. You have to have a place where you can give them that. Leash walks just don't cut it for a young Doberman or any medium to large, high energy breed. You need to love lots of walking yourself. I'd have to walk from here to Miami to give him enough exercise if all I could do was keep him on a leash. We live on 5 acres so he can run around pretty darn well inbetween his real exercise.
Besides giving them good exercise, they need brain work and lots of it. Without both of those things, their health and behavior will suffer. You need to know about the proper and effective way to train and treat your dog or you will have problems...best if you learn a bunch first, regardless of what breed you get or what age.
Dobermans can be outside to romp and play, go to the bathroom and maybe sun themselves for a while...as long as you have a safe yard with a fence. (I don't have a fence, but I live in the mountains....in the sticks) But I tell you what, most of the time, they can't stand to not be by your side. It's hard to go in the bathroom yourself without company and not just company, but a Doberman will insist on helping you through every step of the way. They're right there like a shadow. It can be irritating to some people. This is the way they were bred. Their noses are into everything. They can't just watch you while you cook. They are sure that they should be helping you. It's their "duty." LOL. If you don't include your Doberman as part of the family, inside with you, he will not be happy and will not tend to make as good a protection dog. Anyow, as far as that goes, they really vary. Some don't have it much at all anymore. They've really mellowed them out.
In much of their training, they are very quick at catching on and willing to try (when you rely on positive method training) but they have times where they're sure you've got it all wrong and they are going to show you a better way. If you fight them tooth and nail and get into a power struggle, you'll get nowhere fast. You have to be creative too. Heavy handedness will ruin this highly sensative dog. (some are more sensative than others)
They are monsters as puppies....really....like they're on crack or something. Adorable and sweet, but into everything every second.
Sure they can sleep with you and do anything any dog can do. When you have a trusting relationship and a dog who understands what you want through proper training, you have one of the most loyal, affectionate, trustworthy dogs there are. I love my Dobe. They need rules and boundaries, just like all dogs. But they have to be taught how to do those rules and boundaries. Consistancy and a good relationship are important. Maintaining trust in you is extremely important. But they must be trained in obedience and practiced every day a little bit.
All these things I read about people having aggression problems....it makes me sad. I can stick my face right into Lyric's face and he loves it. (not natural for many dogs) His ears go flat, gets that lovey, affectionate look and just eats it up. He gives hugs and is a big marshmellow. He never looks worried or nervous with me no matter what I'm doing. We lie on the couch to watch TV and I have my legs draped over his side, as there's not much room. LOL. I've fallen on him in the night, in the dark...right on him...nothing. A stranger by accident stepped on his toe when we were at a garage sale...nothing. He knows what I mean when I say, "off" ....as in get off the couch. I never intimidated him to get off. I simply rewarded him when he did. So, he's glad to get off when I ask. If he's hogging up too much room, I tell him, "turn around" and he gets up and rearranges himself so I can fit too. LOL. That was a little trick I taught him.
But he's taken a lot of time, exercise, oodles of socialization, training, classes, lots of patience....it's taken most of my time during the early days to help him grow and be the nice dog he is. Just like children, they need nurturing and lots of it.
If you want a companion dog only and don't want to spend the kind of time and work it takes with a Dobe or a GSD (I've had them too) get a smaller dog who was meant to be a companion and doesn't require all that exercise and only needs a part time job. LOL. I love my little Chihuahuas too. They're adorable and sooooooo easy. So easy to go traveling with, just satisfied with so little. They're wonderful too.There are lots of smaller breeds which are lovely and medium sized ones too.
Spend some serious time, thinking and reading.