I am not an expert in this area but I am coming to the conclusion that if I want to avoid a potential big hassle and claims I will pay for all the extra coverage from the rental car company that gives complete coverage with them with either no deductible or exposure or one that is limited to a small amount, say $100. When I have read the policy that my credit cards provide it really doesn't sound that useful, at least when I rent pick ups or trucks and plan on going off road. BTW I just read my JetBlue Barclays policy and it excludes not only trucks but anything that occurs off road or unpaved road. That does not provide me much in Bonaire or Curacao. In Iceland we spent as much on full coverage as we did for the rental. Who knew volcanic ash damage and chips in paint from all those stones on the road were not covered.
Even when you use a credit card policy in lieu of the rental car, as I understand it you are settling up first with your own money with the rental car company and then you make a claim with the cc and hope to get reimbursed. No thanks. I would rather pay the extra $ and hand the keys over at the end of the trip. That's what we did in Iceland and in Curacao (they didnt' even bother with the return inspection because of the full coverage). I know it sucks to shell out another $100 for the full coverage but it is better IMHO than having to deal with a claim and cc insurance coverage claim.