How does the admission process/requirements compare?
Not sure if it’s harder but it is very tough. When my daughter was starting the graduate phase of her 5 year program her school expanded and accepted 20 students from outside of the program. Over 800 people applied. Ordinarily the school accepts only enough students to replace undergrads who dropped out or failed out.
The 3+5 program is the best way to go as long as the school guarantees entrance to the grad program. starting the two year program is easier if you are coming from a medical career than if you are applying straight out of college. Be sure you have the prerequisite courses and patient contact hours.