Can someone explain how the difference between the job profiles of the two positions- working hours, salary, growth, etc? Which is a more lucrative job for a law graduate?

Salary for all regulatory for a particular grade is almost same. In RBI you start at Grade B while in SEBI at A, so starting salary will be higher in RBI but then promotion is slower there.

Further, RBI legal team has lesser diversity of work as compared to SEBI. But at RBI you can get posted in other capitals while SEBI Legal team stays at Mumbai