Here's a breakdown:
* JEE Advanced: This exam is extremely challenging, focusing on advanced concepts in Physics, Chemistry, and Mathematics at a level comparable to a first-year college course in India. It's known for its intricate problem-solving, requiring deep understanding and advanced problem-solving skills. The syllabus is broader and goes into much greater depth than the SAT. The competition is incredibly fierce, with a very low acceptance rate into top engineering colleges.
* SAT: The SAT is a standardized test used for college admissions in the US and other countries. While challenging, it's designed to assess a broader range of skills and knowledge than the highly specialized JEE Advanced. It tests reading comprehension, writing and language, and math (algebra and some geometry). The math is less advanced than what's on the JEE. The competition is still significant for top universities, but it's not as intensely focused as the JEE Advanced.
In short: If you're strong in advanced math and science and are comfortable with highly complex problem-solving, the SAT might seem easier. But for most students, the JEE Advanced presents a far steeper challenge in terms of content, depth of understanding, and competition.