I can reply with my own feelings on the subject, being in a similar boat as you. I'm about to start my BSN and will start my NP program in 2010. I am leaning strongly toward getting the MSN, and here's why:
1. I'm out of school quicker and working as an NP.
2. There are still not many schools offering the DNP (although it's growing), so I have more programs to choose from.
3. Once I'm working as an NP, I can choose to go back to school later on to get the DNP at a slower pace, rather than killing myself to get through it quickly so that I can start working. (I'm not a patient person )
There you have it... my own personal reasons for wanting to an MSN rather than DNP. I think it comes down to your professional goals and your personal situation!