Diners Club, no contest. I had CIBC Visa Aerogold for 10 years. My travels were frequent, 6 times a year to Europe and the Far East. Hotels, restaurants etc were on this card every trip. Charges would be any where from $1000 to $5000 per trip.My credit limit was 20,000 and my credit as good as it gets. One day some smart security type decided that my restraunt bill for $600 in Taiwan was fraudulent and he put a hold on the card. No one bothered to tell me or my wife. When she tried to use the card it was denied. No amount of talking could convince Visa that I was in Taiwan and had made the charge. She was told that I had to call them myself. Well nobody bothered to tell them that there is a 12 hour time difference as all numbers they gave me were only good during local business hours. Try checking out of a hotel with a worthless credit card. Fortunatly I had Diners Enroute. Needless to say the CIBC visa problems got worse as I went from one incompetent to another. They received the card back in pieces. I now carry a M.C. with the Diners. I do not believe that any single card is good enough to be accepted everywhere, but the combination of these two works well for me.
I have nothing but good things to say about Diners. There is no credit limit, I can vouch for that. I could buy a house on it if someone would take the card. Do not have to pay for 60 days. I have not had a problem collecting on lost luggage or delayed flight claims. I switched cards with no problem. I disputed charges which they have always cleared up for me. I have never had a problem getting through on their lines.
Therefore no contest.