I did geography at GCSE (AQA) and can tell you a little about it.
There is a lot to memorise in terms on content and case studies, specially for the first 2 papers and they usually require the most amount of marks (9 markers). Additionally, the grade boundaries can be quite high too.
It can be also a 'boring' subject (loads of people regretted picking it at my school) however that can be different from person to person. I personally found the subject slightly hard and didn't get good grades in my mocks but in the actual GCSE I doubled my mock grades and achieved higher than I did in any other previous geography assessment. I would also say you could easily catch up on it too if you are behind which is what I would do.
Overall, it really just depends on what you will find interesting as you will be doing it for 2 years and do not want to be bored in lesson as you more than likely won't pay attention.