Every cab can stop by convenient cash machine so you can withdraw money from your US debit card. The drivers know where such machines are located, so you don't waste time after checking in the hotel.
Anotherr thing is that preordering a cab (there are number of possibilities, not neecessarily "minicab" - 7seaters Ad(d)isson Lee? fleet is the most famous company) means that somebody will wait for you, get your luggage, excort you to a car and bring you safe to your hotel for fraction of your black cab fare.