First off, you fight the fight of opinion within your profession in order to have a more unified voice when dealing with the public. Every time I hear a medical student say "their training is just as good as ours" is one time too many. It us in no way equivalent, for many reasons.
Second, there is no PA school where the students take all of MS1 and MS2 with medical students. That is why they wouldn't pass the Steps. There are some where they get a bit of MS2, and very few where they do the majority of MS2 with med students, but they basically skip MS1 and have watered down anatomy and basic science courses. Their fund of knowledge is lower, thus their eventual understanding of cases and literature is lower. You can't say, "but what about the exceptions, the ones that work really hard" when comparing them to us, because in medical school and residency, there is no option for us to not work hard. Their best can barely scrape the abilities of our worst, hardly an accomplishment.
Now, as to the fields where they are making inroads, there have yet to be direct comparisons of unsupervised midlevels taking care of cases in equal acuity to their physician counterparts that show equal outcomes in any field. Anesthesia and primary care studies have, by and large, focused on low acuity or supervised practice. I just hope we get some honest studies in the future and the public wakes up.