Defunding police can be beneficial. Defunding police can locate money to other areas that can benefit a community more, such as giving more money to health facilities. This can take situations away from police that are better suited for professionals in an area, such as social workers and other people who are better trained in helping the mentally ill or abusive situations.
However, in some places, defunding can be detrimental. In areas with heavy crime or smaller areas, the police might already not have enough funding and defunding could cause the force to be overrun due to decreased resources. Without enough resources, crime can increase due to people taking advantage of the situation.
In terms of abolishment of police, this would not be a good situation at all, because in the transition period between finding a new system, there would likely be many people taking advantage and committing crime with out prosecution. Also, a new system could be faulty because it is hard to tell how well it will work.