There aren't many differences between college and sixth form.
Most sixth forms are 'attached' or part of, a school, whereas colleges only really teach 16-18 year olds, and others in A Levels, AVCEs, GNVQs and other qualification.
There is no real disadvantage of going to either a sixth form or college over the other.
However, many would say an advantage of a sixth form is that you know the teachers, and students - so it's much easier to socially adapt to sixth form.
Yet, in the favour of colleges - you get to make new friends and impress new teachers. So the choice is up to you!