There are mainly 3 engineering entrance exams in India for candidates looking forward towards top engineering institutes in India. It includes JEE Main, JEE Advanced and BITSAT. Frankly speaking there isn’t much difference in the syllabus of all these entrance exams. The main difference is BITSAT focuses more on the candidate's speed and accuracy and on the other hand JEE focuses more on deep understanding of concepts. Furthermore BITSAT includes English & Logical Reasoning as well which is not the part of JEE.
JEE Main and Advanced -
JEE is slightly tougher than BITSAT as candidates need to have thorough knowledge of physics, chemistry and mathematics subjects. The set time for any BITSAT candidate to mark the right answer is approx 72 second which is about 2 min in JEE. So if you’re preparing for JEE then you’ll automatically cover all BITSAT syllabus as well, but keep it in mind that you need to prepare for English & Logical Reasoning as well and for that you need to plan your time table accordingly.