I've tried twice to convert from dual card LTF to visa, but they rejected both times.
Visa is much better than dual cards imo since you get bookmyshow instant discount (I still haven't got the amex cashback for the ticket I booked 2 months ago, cant be bothered to talk to customer support for it), lot of lounges don't accept amex cards and even those on the lounge list sometimes have issues with the amex card.