The people defending Amex are doing so with rose colored glasses. I have been on both sides of the dispute, I used to work for Citibank and I am an Amex plat card holder and I was shocked with how poorly Amex represented its customers in disputes.
In my experience, I finally resolved it, with much much more legwork then necessary. My wife ordered some stuff over the telephone, via an automated system (which I wasn't a big fan of). However, she ordered the product advertised. At the final confirmation menu after she entered her card number, it tacked on the item twice and some other services which she did not sign up for. She tried to transfer to a customer service agent, however she just got an automated "goodbye." She tried to call many times with no success, and we googled the company with the same scam happening many times. Of course, I told her not to worry, you put it on your Amex plat, they will work it out. They told us wait for the billing and to resolve the issue. We did, we had a lot more charges then we authorized, and disputed. We now found a number in our shipping to talk to a human in the system. We called the vendor, and the human basically stonewalled us, and told us we could return the items, but there would be a return fee. the return fee was more than the cost of the items! (it was like $60 bucks per item). So we opened a dispute with Amex.
Same process, dispute, taken off. Then amex reversed it, and said they sent proof of the charge. They sent it, and the only thing they had was a poorly printed out e-mail from the vendor with an itemized list of fradulent charges. No signature, no voice verification, no CVV. I had to go through multiple calls, fortunately because of my diligence and documentation Amex took the charges off and I mailed the product back.
In the end the work involved was waaaay more than Citi ever required. And I felt like amex was never on my side.
Amex does not side with the customer in these matters, and its soured my view of them as a card issuer.