I took anatomy and physiology II before I took anatomy and physiology I. Part I was harder I think in that it was more time consuming because there was a lot more memorization with bones, prominences on bones, muscles, attachments, and so forth. A lot of that for me disappeared from memory as soon as the test was over, and I'm ok with that. Physiology is the interesting part for me. I'm ok with just knowing what the bone is called and not what the name of every feature is. That said, part II was more interesting and probably easier due to interest because it dealt more with physiology.
I've never had two courses in general biology (school didn't offer them), but I've taken vertebrate zoology, microbiology, botany, and several other environmental and ecological classes. I didn't think any of them were hard. Acutally I'm in botany now (six years after finishing my degree), but it's cake. All that said, even though I took several upper level biology electives in college (out of interest) I took a course in biology for nonscience majors one sememster just because I needed a three hour class offered at that time of day. It was hands down the hardest biology I've ever had. I'm not sure why either, but the tests were a *****. I'm taking genetics and cell biology soon, and based on what I know now I don't perceive them as being all that difficult, but that one bio course was rough. I made a B in it and was glad to get it.