Bull mastiff or great dane?

Research both and talk to some breeders to help you decide. Both are quite large, although the dane will be taller and the bullmastiff will be more broad. They dane will drool a little less. Both breeds have high incidences of heart and hip issues and also sometimes wobbles, which is more prevalent in danes and is a neurological problem. Both will require ongoing obedience training and an owner who will give them rules and boundaries.