MHO: I don't think taking on a travel card with a bonus will hurt you even if you plan to buy a house within a year or so. Because there is already a question about applying for a card here. A good start bonus with an annual fee waived gives a terrific mental boost, also.

IF those cashback points seem more valuable because you won't be traveling, that's one thing. But, if you plan to have a trip in coach after a few years, the Amex ECB doesn't really further the cause. Again, unless you are short term in thinking that the cashback is better for your budget for now.

Back to the bread trail for either the Arrival or Chase. I think I would go with Chase for the versatility of the UR. (Disclaimer: I don't have either card). Best wishes!