1) I am high volume Option Writer with huge amount in Margin withhold and transact for premium earning on invested margin. On Expiry Thursday when my money get released, I can put withdraw transaction on Friday(although that money comes to trading account by Friday morning) that money get deposited on Monday to bank and you lose the 3 days earning on that. If the same you do it with ICICI Direct or AxisDirect you can buy Friday morning Liquid Funds(which gives almost FD rate interest) and it is bought with Thursday NAV. for 1 crore you lose 2000 Rs per day or about 6000 in 3 days .
2) With Zerodha you get ripped off with 0.5% of brokerage for physical delivery settlement. All brokerage houses charge much lower like 0.1% to 0.2%.
For 1 option lot with underlying value of 10 lakh and your margin investment of 1.5 lakh there is just brokerage of 5000 to zerodha in addition to NSE charges, auction penalty which is much less.
3) In one of my high value cash withdrawal to bank they did not process on thursday and regretted for which I lost 12000 in 3 days money stuck with them - So hopeless they regret for their error and customer loss.
Zerodha gives you less brokerage on regular transactions but rip you off wrongly. 20 Rs or 30 Rs brokerage does not matter but when you get ripped off once in 1-2 months like this you lose the advantage of lower brokerage.