Hi, I do both geography and biology.
GCSE geography just scratches the surface to what you learn at ALevel. Alevel geography goes into much more depth and covers much more geopolitics and even some economics. It's very interesting and really pushes you to have more global understanding-which I personally like. Both human and physical geography have really interesting aspects that is so unique to many subjects.
You say that a con of biology is long answer questions but geography has MUCH longer answer questions than biology does! Geography has essay elements to it, in the form of 8,12 and 20 markers!
Biology is also a great subject and if you enjoyed it at GCSE you are likely to enjoy it at Alevel as it has similar concepts but in much more depth, detail and as you have probably heard before- much more content heavy! However, that shouldn't worry you because it is a great subject and if you understand the concepts and can apply it you won't struggle as much. Long answer questions are not really present in biology except for 1 25 marker in paper 3. Other than that, it's mainly shorter answer questions- geography is definitely more essay based/wordy than biology!
Also, just so you are aware, if you are wanting to do medicine, biology is not usually required as long as you have Chemistry and another science (could be physics or bio), so chemistry is the only one you are REQUIRED to have if you want to do medicine.
Both subjects are great, and it's a shame you are not doing both- maybe I'm a little biased!! lol :-)