PR math was VERY easy, so it doesn't help you learn or handle tougher questions. PR Verbal was hard, but not because it was well designed, but because the questions were asked in a very vague way and the answers were very suspect. I never "argued" with the official answers of the OG in all my missed questions, but I disputed more than 3 or 4 answers in the PR Verbal section when i took it (and got the lowest verbal score I've ever received in practice, V33).
That's why I stopped taking PR tests and focused on
MGMAT CATs (and GMatPrep/PowerPrep), because while
MGMAT CATs had insanely hard math, the scores were somewhat reflective (add 2-4 pts to your Quant score) and the verbal was mostly well designed and about the right difficulty.
Hope that helps!