Compare what the same monthly amount could grow to via a SIP versus an FD/RD, at your own assumed rates.
SIP maturity: Standard SIP future-value formula
FD/RD maturity: Standard Recurring Deposit compounding formula
Is a SIP always better than an FD?
Not necessarily — a SIP has a higher expected return over the long run, but no guarantee, and it can lose value in a bad market. An FD guarantees its rate but usually loses to inflation less dramatically than it beats it. Most financial planners suggest holding both, matched to different goals and time horizons.