If you're going to use it for travel at all, especially international travel, go with American Express. There is an annual fee, but I've used mine to get out of some real hell-holes, never with any problem whatsoever. Well, except one time in Cyprus when their computers were jacked up, and the hotel wanted me to get cash to pay my $1200 bill. Nyet. I ended up calling AmEx myself in the states, and putting them on the line with the hotel manager, and giving them a verbal authorization for the charges. Everything worked out, and when I got home, there was a very nice letter from the hotel manager apologizing for any inconvenience, and offering two nights free at the hotel. Of course, I haven't been back to Cyprus since.
Do not carry a balance on any credit card. Ever.