I would say that PP is easier than the real thing depending on whether you studied the official guide. If you had 700 in PP and did not go over the official guide, then it is a reliable score. The only thing is that no test preps really cover Perm/Comb and Prob. questions. I agree that if you want >740, in the 46+Q, you will get a few of those question types.
Barron was a waste of money to me. I tried their CAT and it was not only fraught with errors but full of glitches. IMO, there are much better test prep material. As fas as Arco is concerned, I only did their paper test and their scoring algorithm is much more lenient than the Kaplan
/PR score. If their CAT is same, then you should review your score downward. I believe PR CAT to be a quite reliable predictor of your actual score.