GRE is a bit tougher when compared to SAT. It includes a verbal reasoning section to assess a student's reading comprehension and reasoning skills, which is not there in SAT. Also, you will not come across a dedicated analytical writing section in GRE. The math section of the GRE is more complicated than SAT, and unlike SAT, there is a quantitative reasoning section in GRE. So, the syllabus is not similar to SAT.