Zerodha, without a doubt. I initially started with Groww, but within 1-2 months, I had to switch. Once I tried Zerodha, I never looked back. The features, support, vision, transparency, ease of use, and much more that Zerodha offers are unparalleled and unmatched.
I have tried other brokers like IIFL, angel one. Ease of use, features, support process, educational content, (marketing email content etc {very less in Zerodha which is good}) all are best in Zerodha only.
If you’re looking for automating/backtesting as well, then streak+zerodha integration is one of the best I have found.
Because TV Library has a feature of DOM based trading. You can have a wide view of the orderbook. It helps me to quickly scalp the order book instantly without pressing any button other than the price on DOM. Managing positions on the chart is also easier for making use of the momentum burst in OTMs.