Given that the guys who write the UK ATPL examination question bank use the CRP-5, it has to be worth the few extra quid (£) to use the same tool in order to achieve the same level of accuracy as the guy who's asking the questions.
How badly do you want your ATPL? A failed exam will mean that you will have to cough-up another £68 for a re-sit of that exam.
By comparing two different whiz-weels I've seen consistently different answers to questions from the question bank. Sitting in an armchair at home, without any time pressure, the accuracy is going to be as good as it gets... but two different answers aren't acceptable. Therefore, it's a no-brainer... if you want to pass your ATPL exam, use the right tool for the job!
If you consider that you'll never use it again after the exams... flog it on EBay. My CRP-5 is in the bottom of a box somewhere in the loft!