All dogs are different and all breeds have certain attributes in special areas not just mentally but physically as well. I think they should have a variety of different breeds available to them and use the breed that the current situation requires since anything could happen in that line of work.
No, police should not select other types of dogs to be on the police force, because the dogs that they use are very effective. The dogs that they use are good at tracking drugs, and they are also good at attacking people trying to flee from the police. There is no reason to use any different dogs.