There are far more solicitors than there are barristers, so naturally those who study for a PGDL are more likely to end up as solicitors and not as barristers, and that's what most of those taking the courses intend. The qualification paths of people who aren't competing for the relatively small number of pupillages have no bearing on your prospects of success.
Of greater significance is the overall attrition rate amongst aspiring lawyers of every kind. Most people who seek to become practising solicitors or barristers do not succeed in that aim. Most people who pass the Bar exams don't become practising barristers. Some become solicitors.