Certainly, I didn’t think my AP tests/classes were that hard (I took 10 AP exams total [6 during my senior year] and passed them all) but some of my peers, very bright students who were used to always getting high grades, struggled a lot through our AP classes, especially Calculus…

But, like most people who’ve taken one type of test, I haven’t taken the other. I can’t attest to the difficulty of the A-Levels. If I had to hazard a guess, though, I’d say that the A-Levels are harder. I resent people saying it, generally (lol), but from what I’ve heard the education system through all of Europe, and including Great Britain, is a fair bit harder than it is here. I really don’t know.

I can say for the AP exams that I didn’t know my material very well, but I still ended up with all passing scores. I passed my Latin exam with a 3 this year even though I knew almost nothing about the Aeneid, except a few plot details in English. I passed Statistics with a 5, even though I don’t know how to carry out any statistical tests without a calculator, and I probably remember very little about statistics now, about 2 months after I finished the AP course. I passed US History with a 5 even though we hardly even covered any topics past 1910 in class. I only spent a few hours studying for it, despite the lack of coverage of many topics in that class. I passed Chemistry with a 4, even though we only did 3 labs during the entire year, and I didn’t care that much about the course. I’m not sure if I should have been able to pass these tests with so little knowledge, even though I am certainly glad I passed them and got college credit.

All things, said, I don’t know how you are going to get an accurate answer to this question. You need to talk to someone who has attempted both types of tests. That person would be extremely difficult to find, if he/she even exists.