I have been preparing for the GMAT for several months now. I have found that the KAPLAN
books are generally more rigorous, furthermore the free CAT tests you get with the KAPLAN
book are much harder (for both verbal and quantitative) than the ones from princeton review
. I haven't tried ARCO, so I really can not give you any info on that. I hope this helps....Good luck!
"No! Try not. Do. Or do not. There is no try.