Personally, for my certification renewal, I did last year I took the full VCP 6.5 exam, as others that I had spoken to had suggested it would be slightly easier. Whether this is actually true or not is debatable.
If you are thinking of using the Full VCP exam as a backup, then I would highly recommend to review and compare both exam blueprints. Without looking myself, there is a chance some objectives on the Full VCP exam do not appear on the delta.
Best of luck anyway. Hopefully, you will pass the first time around.
