I'm an American and regarding AP courses in US High Schools, they're probably less in depth than A levels. However, the structure of the class is different so even in some of the easiest APs most teachers will assign hours of homework to do everyday. I definitely wouldn't say they're harder and the content itself isn't particularly difficult, but the courseload is a lot of work and grading is based a lot more on projects throughout the year instead of tests. For honors courses . . . they're a joke, in comparison to A-levels the classes are ridiculously easy and barely cover anything. I know this is kind of a long answer, but to answer your question: A-levels are harder, but the teaching style is completely different. Regarding whether or not you should go to the US, I would definitely suggest it because US students typically have higher chances of getting into US college and most US colleges would prefer more well-rounded students, which they can't really get from A-levels. It depends greatly on the US college, but going to the US would likely make your chances slightly higher for getting into a US college as well as acclimate you to the United States before you went there for college.