Kaplan Exam Kit or the BPP Exam Kit

I’m currently using Kaplan Study Kit for my F1. The book however is the one published in 2015. Currently, after completing some chapters in the Kaplan study book, i practise the question in the BPP Exam Kit (2017). However, I hardly am to do many question correctly. Should I stop studying the outdated Kaplan book and start afresh with the BPP study and exam kits?? or Should I continue with the Kaplan Study book and simply use a Kaplan Exam Kit instead of the Bpp one?? I really want to score very high marks for the F1 exams.
Any comment or advice will be much appreciated! Thanks in advance.