We've been going to SXM for a long time. Used Hertz one of the first times there. We arrived and they had no car for us as promised. We had to pay a lot more from another company and contacted Hertz when we got home to complain. Got the "they are independent" not part of Hertz, USA story. Pushed harder and eventually got reimbursement for the difference from Corporate Hertz (Hertz SXM did nothing).
Moral of the story? Good and bad stories with any car rental company so use one you trust.