I got A/A* in 11 out of 12 GCSEs, and as above poster said, I hope Im allowed to answer too.
I find A Levels a lot harder, as theyre more independent work, require a huge amount of motivation and dedication and you need to stay on top of everything, otherwise youll drown in a pile of work, revision and coursework. A lot more content, exam technique is harder, mark scheme is more specific and requires a good base of understanding from GCSE.