For RNs wanting to pursue a doctorate, it is important to pick a degree that best matches your anticipated  career path.   The shortest simplest explanation of the difference in these degrees is probably:

1. PhD – If you want to be a nurse scientist & teach in a university & conduct  nursing research. 
2. DNP – If you want to be an advanced practice nurse, who primarily uses research in leadership, QI, patient care, etc. along with measuring project outcomes.

An excellent, free full-text, critique can be found at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4547057/  

Of course, some DNPs teach in universities, particularly in DNP programs.  PhDs may otherwise be better prepared for faculty roles.  I encourage you to look carefully at the curriculum at the school where you hope to study and expectations of a university where you hope to teach.  Speak with faculty,  & choose wisely.