Get a quotation from different banks. Choose the one you like.
People choose preferred banks because of different reasons. For example Suzuki and Bank Alfalah, BOP, BAHL, HBL have collaborations for priority deliveries And some promotions on registration and insurance aswell.
Some people choose a bank where they are already maintaining a bank account.
Ease of payments etc.
Meezan bank bears withholding tax because the car is registered on the banks name. I think most or Islamic banks would do that.