The PR “top” book has a bunch of lists - some are academic like good schools for this or that major, and some are things like schools for sports, parties, environmental awareness, etc. My perception is that the PR uses quotes from students more heavily. Each school gets a two page spread with school stats in the outside margins. The format is consistent for easy skimming. I don’t own the complete guide.
The Fiske guide is more detailed - they cover a school over more than a two-page spread, so there’s a chance to mention unique programs. The ratings are on a scale of 1-5 (PR uses 60-99, so a little more fine-grained.) There are lists of affordable schools and schools for popular majors, but overall fewer lists than PR. The tone is more like what a teacher or guidance counselor would say, though students are quoted in this book as well.
They are both useful books. It’s just a matter of what style appeals. You want the book your sister will read. You might try the library as a place to compare them if you don’t have a good bookstore.
With either book, you’ll be looking at just a sample of schools. You will still need to investigate your state system (unless your state flagship is one of the best in the country it won’t be in these books) and regional options.