First off I am in Connecticut. I am in a diploma program here and I will have the same RN license as anyone else who went and got an Associates Degree or BSN. BSN's are usually needed when you want to move up from clinical work into management. Although there are some specialties that like the BSN, but it is not required.
My A&P professor, who is the advisor for the Hospital based program I am in, said the Associate Degree or Diploma nurse will make the same amount of money because they will have the same RN degree. The same NCLEX-RN is taken no matter what your degree is. As a matter of fact the same BSN degree nurse will have the same RN degree, but will have more avenues open.
Again, I cannot speak for your state, but in CT a diploma vs Associates is no different pay wise or opportunity wise. The only difference with BSN is more opportunity. To be certain, check with your state nursing office and ask them.
Also, if your diploma program your interested in is hospital based it is probably a great program. It has probably been around a long time too - my school is over 100 years old.
Best of luck
Here is a link to Missouri nursing organizations