After having worked through the majority of the quant in the OG and virtually no verbal, I noticed approximately 2 quant overlap questions in each of the powerprep tests I took, and 1 or 2 in the Verbal section of each powerprep. I did work through all quant and SC in the two smaller books as well. I thought the practice was still useful and Im sure my scores were slightly schewed in the quant.

I would agree with Eric, take one and then work through the books and take the second one.

which OG are you reddering to drhomler?

I have been using OG11, including the verbal and quant supplements. I feel as if there were a few overlaps in the GMATPREP as well, definitely that number line one where you have 1/5 and 1/7 hash marks and they want to know what the smallest distance between the ticks is, although I think it was presented in a slightly different manner.

Since I dont practice RC and very few CR I didnt notice anything there in either the Power or gmatprep.

I thought the SC was much easier in powerprep and that was the huge difference in my scores between the two, on both powerprep tests I scored 42(95%) and I have never scored that high on mgmat(41 was the closest I came) and on GMATPRep I think 37. For me the swings in the scores are all about how well I do on the SC I consistently miss the same amount on the CR and RC.

Incidentally I take this thing tomorrow so I hope to writing a positive(for me) debrief over the weekend.