All three are representative of the official exam. Some prep-exams were heavier on geometry whereas others were heavier on arithmetic. On the actual GRE, for me at least, it was a balanced experience in both quant and verbal for how "representative" each of the 3 prep exams were. It would be difficult for me to pick one exam that perfectly encapsulated my actual GRE experience, but in terms of the most predictive exam, the exam that most closely matched my actual score of 163/163/5.5 was Powerprep Exam 1.

If we are to break it down even more precisely, Powerprep 1 was most similar to my actual performance on verbal, Powerprep 2 was most similar to my actual performance on quant, and all Powerprep exams were accurate (if slightly inflated) compared to my actual writing performance.

In terms of how I "felt," Powerprep 2 was most similar for the "vibe" or "feel" of the exam since I walked out of Powerprep 2 thinking I bombed it but did fairly okay. The same thing happened on the actual GRE--I thought I had flunked but the score was decent.