This is my opinion:
Usually people will say pick the highest reward/cashback card. But, I believe best card decision can be fulfilled based on the redemption rather actual reward rate.
For some people 24% airmiles no use when compared with 5% actual cashback on statement, it all depends on their requirement.
You're comparing reward card (with best possible options of redemption as hotel/airlines) with pure cashback card (each serve different kind of people).
Regalia:
Amazon - 6.6%
Flipkart - 3.9%
Vouchers - 6.6%
Flights - 6.6%
Hotels - 13.3%
(above percentage is when that person redeem those reward points to Flights and Hotels)
vs Cashback:
with 5% statement cashback in above categories.
Also, as mentioned by
@bugmenot there is lounge support with priority pass for add-on holders too.