JUst my two cents worth on an sometimes overlooked factor. I had to do dispute resolutions with both Amex (KF Gold) and Visa (Citibank Plat) and Mastercard (German LH M&M version) I can only tell you that both Visa and Mastercard are very poor in my view how they handle such disputes.

Amex credits back the amount, contacts the vendor, discusses the issue raised with the charge and overall supports you as a card holder quite well. Visa and MC ask for tons of paperwork, do nothing for weeks and come back saying they can't do anything and that one should take legal (civil court) action. Utter rubbish. This may sound like something not important but it really pays when it happens and is needed.

That's why I stick to KF Amex Gold and Citi Visa Plat combo. Yes not the most optimal version but I don't want too may cards and I really appreciate Amex service which has come through 3 times now on disputes.