We preferred and use Carmel, and would recommend Carmel coming from EWR into Manhattan. Both have their own holding or staging area for fleet cars off the airport, and they are usually curbside in 10 minutes - which is typical walking time/distance once you are off the jet/inside the terminal with carryons - or, from luggage carousal - after calling them. They have the free App for iOS & Android to keep track of the reservations & status, etc.
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Have Dial7's phone #'s to call or use as a backup - both have online/coupon discounts.