1) Distance learning requires self-motivation and can be conducted at your own pace. Full-time is classroom based and on a fixed timetable. Think about how you will motivate yourself and whether you want to work while studying. DL can be harder in that it takes longer to get answers to questions that may arise and I would also say that good training manuals are more important than if you are on a full-time course.
2) Why have you chosen Bristol or OAA? As I said above consider which training manuals they use and where they are based as there is a full-time element to every course.