Ah the old Associates vs. Paramedic dilemma. In Ohio (and perhaps nationwide), there is a big push to transition all paramedic programs to degree programs. There are still a lot of non-degree programs out there, though.
In all honesty, I doubt that very many of your credits will transfer to a four year school. Many nursing and paramedic programs have chemistry, biology, A&P classes that are geared toward those professions. Typically, these courses will NOT count as the medical school pre-reqs. (And therefore, probably not count toward a degree in Bio or Chem) I took an A&P class that was listed as a "Fire Science Technology" course - I referred to it as A&P for Dummies. It was not even close to being as difficult as the nursing A&P or pre-med A&P. Probably the only courses that will transfer to a four year degree would be English and Math.
As far as a four year degree and med school - the word I got from a couple of Deans was that they really don't care what your degree is in, as long as you have taken (and done well in) the pre-med courses of Biology, Organic Chemistry, Physics, and Gen Chem. As a side note, art history and foreign language majors have a higher percentage of applicants admitted to medical school than biology or chemistry majors.
That being said - if you decide to pursue the four year EMS degree, make very sure that you are taking the Biology, Chemistry, Ochem, and Physics classes that are required for degrees in those majors (or are listed as the courses for pre-meds). These will most likely count toward your EMS degree, but the science courses recommended for your EMS degree will probably NOT count toward med school pre-reqs. At many schools (not all), even the nursing majors do not take the biology and chemistry that med schools want.
In the grand scheme of things, if you really want to be a paramedic, but aren't sure about going on to med school, take a certificate program, get out and the field and get some experience. Don't waste the extra time on the paramedic degree. Then - if you decide med school is what you want, you can go to a four year school and get the classes you need.
Good luck!!
Amy