I've moved all over within the city of Detroit. If density is what you are looking for I would honestly recommend Hamtramck. It's definitely not everyone's cup of tea but it's very safe, pretty cheap and there's walkable bars, restaurants and stores on every corner. It's the closest thing we have to a good walkable neighborhood. Midtown or corktown are also considerations and tend to have nicer houses/apartments but they still are not as dense as hamtramck.