There is no such thing as bully kutta...as per me its all made up. In India we have The Tibetan Mastiff found in higher reaches of the Himalayas and the gaddi dog found in Himachal. But both are not suited to city life and hot climate although people may have kept them.
As for dobs, any breed that gets popular starts getting breed my nearly everyone to make money and that is when problems occur. There is nothing wrong with American lines or american dogs. What you have to do is buy from a very reputed breeder, study the breed and about the health issues and if required get a health scan done and speak to other puppy/ dog owners who have bought dogs from that breeder. A good breeder will not have any problems disclosing such data. Do not buy a pup out of parent just imported as one will not know the health or temperament issues. As far as I know dobs have always been know for being a one man dog and at times unpredictable, but then that is also because they are a guarding breed.
Great Danes are nice also but need proper training to be under control always plus you have to keep in mind the food cost and the medicine cost which will also be extra due to the size, apart from space and exercise required.
A Indian breed / stray dog adoption is a good idea and they make very good watch dogs. Get a pup from a shelter and they usually neuter it and give it to you. They are much healthier dogs and now a lot of celebs too have Indian dogs/ stray dogs as pets.
Adoptions at the Sai Ashram Animal Shelter, we have many pups and adult dogs for adoption. Visit https://saiashram.blogspot.com /
for details and pictures.
If you want I can also send you their contact number etc.