Med school vs pa school?

Experience as a PA would likely be well regarded on a medical school application. That being said if you want to become a physician you should apply to med school for a few reasons. The first is that you would still need a very strong MCAT score. This will be much harder to get while working as a PA as you will not be fresh out of the classes being tested unlike 99% of others taking the test (which you will be compared with). Also if you plan on working in between you will have much less time to study for the MCAT compared with most others. The MCAT tests basic science material, not medical knowledge so you will not be caught up with the material after years spent focusing on other things. While you can take to MCAT to get into most PA schools, the test scores are only accepted for 2-3 years after you take it so they would no longer be useful when applying to med school.

As well as this, many medical schools require that prerequisite classes be taken within 5 years of applying. This would likely mean you would have to quit your job and attend a few years of undergrad again to be eligible for many programs.

Finally after all this work, you still would not be guaranteed a slot. Most medical schools only accept less than 10% of qualified applicants. Being a PA may help your application, but GPA and the MCAT are still much more important. You may do all this work, quit your job, retake classes, spend months dedicated to studying for the MCAT, and have nothing to show for it. If you make it in you would still have to go through 4 years of medical school and 3+ years of residency (and potentially more of fellowship depending on your specialty).

While it is possible to go from PA to MD, it would be much better to go straight to being a physician if that is what you ultimately want. You can always apply to PA schools as a back up.

If you want to be a doctor, just go to medical school from the start.  That's by far the more straightforward path. 

If you do become a PA first, then your PA experience and education will likely be considered as part of your admissions decision.  But your grades in your med school prerequisites will still be examined, your undergraduate GPA will still count, and your MCAT will still need to be good.  

You will still have to complete the full medical school curriculum.  It will be a full 4 years of medical school for you, and then you will have to complete a residency after you graduate.

Medical schools will look at your undergraduate and, possibly your graduate, GPA and your MCAT score.  They will consider your paid work as a physicians assistant as experience, but it won't make up for a poor GPA or low MCAT score.  And, yes, you would still have to go through all four years of medical school, plus residency and fellowship (and get licensed) before you cold practice as a physician.

The standard advice is that if you want to be a doctor, aim for that from the beginning.  If you are unable to get into medical school, you can try for a Physician Assistant  (PA) program.  If you don't think your grades are good enough or you simply don't want to invest the time or money to earn an MD, going into a PA program is a faster way to be caring for patients in a clinical setting.  You sill have to get your 2000 hours or work before applying to a PA program and you sill have to have some very high grades in your prerequisite courses.