I would look for a yellow cab, and if you don't find one after 5 minutes, hop on the subway.
Subway is the quickest and most reliable mode of transportation in Manhattan.
The E, A, C, 1, 2, 3, 4, 5, 6, and R trains all stop in the Financial District.
I dislike Uber.
Uber can charge your credit card whatever they want, and you don't find out until after the ride, via email, after they already charged you.
I was overcharged a couple times, and they wouldn't refund me. Bastards.
I don't have experience with catching cabs in the Financial District, but they're easy to find in Midtown.
(EXCEPT: when it's raining, during rush hour or during UN week or Pope visits.)
I feel that yellow cab drivers are even more appreciative when you ride with them, since less and less people are using them.