Sixth form.
Colleges may be more independent, but it generally means that they aren't so fussed about you, especially when it comes to applying to university.
Loads of my friends were attracted by the option of a new environment at the various 6th form colleges in the area, they went and don't really like it that much. I stayed on at sixth form and it was the best decision, it's a lot different from school and because you're returning to a roughly similar environment it means you can focus on getting the work done rather than settling in.