Instead of comparing NP school to PA school, it would be more useful to decide what your career goals are. What kind of work do you want to do? Where do you want to work? What patient population do you want to treat?
A key difference between NP and PA school is that NPs must declare a specialty immediately and the education is focused on that specialty only: Acute Care Adult/Geri, Acute Care Peds, FNP, Primary Care Adult/Geri, Primary Care Peds, Psych, etc. A PA receives training in everything and is most comparable to an FNP, except FNP is considered Primary Care.
If you aren't sure if you want to specialize, then go for the PA.
As for the science courses, an NP has already taken undergrad science courses, plus BSN patho, etc. One has to have an anatomy, physiology, microbiology and chemistry courses to get into BSN programs. Then the MSN NP training is advanced (graduate) patho and pharm. An NP student is expected to know anatomy, physiology, and microbiology already. With regard to anatomy, experienced MDs have told me that even recent med school grads can be weak on clinical anatomy.
As far as EKG interpretation, all RNs and NPs receive education on this. Individuals who work in cardiology will receive extensive OJT plus there are many workshops available on this topic.
NPs, PAs, and MDs all have the same treatment approach: assess, diagnose, treat, and follow up. Supposedly NPs have a more "holistic" approach, but in today's climate where all providers have to see 3 or 4 patients per hour, it's not really the case. Personally, I do think the NP role, which requires the RN as a prereq, attracts a different personality type. The nursing model is based on caring, not just on treating.