I reviewed all the geometry concepts in The Official Guide to the GRE General Test last week, but felt not enough, therefore checking out the geometry concepts in ETS Math Review Guide. But all the content looks quite the same to me, if not the exact same. However, I did not check page by page.

Anyone knows if there are any differences between the two? If not, I do not want to waste my time re-reading concepts in the ETS Math Review Guide

They are exactly same, Math review guide will only provide you with some extra questions to solve. You can look into greg mat quant concept series or khan academy for more resources.

The 3rd edition of the official guide appears to have all the same exercises that are in the PDF version of the math review. If you saw extra questions on the math review, could you specify where?
I would prefer to use the physical copy to read the math review. However, I noticed that the math review PDF is 198 pages long, while the math review section of the official guide is only 68 pages long. Perhaps this is because they fit more content per page in the official guide, but still, the PDF is 3 times longer.
Thus, I am kind of worried about missing something if I use only the official guide. Does anyone know for sure whether or not the two are identical?