Once you've done a few training kits and actual exams, it is apparent that the people who write the training kits don't talk to the people who write the exam questions, and may not have taken the exam themsleves. Instead, Microsoft publishes a list of topics that will be convered on an exam, and Training Kit creators create training materials than cover these topics. This is because Microsoft wants people who actually have experience with the product rather than just crammed for the test. There is no promise or guarentee that a training kit will contain the answer for every question on the exam. If you're very experienced in all topics that are on the exam objective list, you probably don't need a training kit.
That said, I've just ordered the 70-463 book myself, because that will be my next exam and I've at little exposure to data warehousing in my career. Hopefully, setting it up at home and trying out the scenarios in the book will help me get familiar enough with it to pass the exam.