Though this may be true in general, I still find many Visa/MC-only merchants for large purchases, such as furniture stores and landscape companies. Examine your own spending percentages before deciding that Visa/MC won't account for much.

For example, Amex accounts for 70% of my activity if I only include normal monthly expenses. But when I add in large house-related expenses that can only be charged to Visa/MC, Amex accounts for only 40% of the annual bill.

So if you're in a situation where Visa gets 60% of your miles, it's important to put some effort into picking the best Visa/MC card.