I'd definitely go with hotel credit cards instead of airline credit cards. I used ot have a CO Visa, Marriott Visa and Hilton Optima. Gave up the CO Visa when I realized how useless CO points were when you actually wanted to redeem them for something besides a round trip to Cleveland. Hilton and, in particular, Marriott, have been far easier to deal with when it came to getting free stays in Europe.
The Hilton and MArriott cards also give extra points when you use them as their properties. CO, at least, didn't give extra miles for charging CO airfare on the card.