I go to a sixth form but I have some friends who go to college, so I have an idea of the differences. Basically, sixth form is basically like school but with no uniform, you have frees and the workload is higher. However, at a college you're given a lot more freedom, like no dress code and you'll maybe have less contact hours so you'll have to do more work at home. Also, there will be lots more choice in courses at a college, like they'll offer Btecs or the IB there as well as a wide range of a levels, whereas most sixth forms only offer A level courses. I would recommend attending some open days at some sixth forms and colleges so you can get a proper feel for them.