You can become a NP with either a masters or doctorate (DNP). You have to compare the job of a nurse vs NP and decide which one is better for you. There are differences.
If you are asking which is better- masters or DNP- the answer is that it doesn’t really matter. Both lead to NP.
If you want to teach or go into research, you can get a PhD. You can also get involved in research with the other degrees.
The DNP degree requires approximately 2 years to complete, depending on the program.
I don’t know of any DNP’s who call themselves “doctor.” All of the NPs I know or see (masters or DNP) introduce themselves by their first name, even in a professional setting. Similar to PT- the DPTs I know introduce themselves by their first name.
If these professionals wanted to be a MD, they would have gone to medical school.