Listen to this gentleman here, he's making a good and subtle point. I am a PA for the last 11 years, now a 3rd year medical student. You can become very well differentiated and knowledgeable as a PA in your particular field. As your expertise grows, your attendings will come to trust your judgment and abilities to provide care at a very high level (often indistinguishable to what they can offer procedurally). This has been my experience certainly. But as the gentleman above already mentioned, the ultimate call rests with the attending you work with, as it should. So I wouldn't worry about not having enough scientific knowledge to care for people, that's a complete non-starter. You will learn what you need to know to help people well after PA school is over. Make no mistake, PA school is rigorous and demanding, but medical school is a whole other level of pain. I decided to go on because I love the practice of Medicine. There is nothing I like doing better and I wanted to do it at the highest possible level. I can honestly say, being a PA has been an invaluable experience towards this goal.